Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$138.64	9.694%	$152.0798	$152.08	$152.10	$152.10
Purchase #2	$178.70	12.242%	$200.5765	$200.58	$200.60	$200.60
Purchase #3	$168.56	12.774%	$190.0919	$190.09	$190.10	$190.10
Purchase #4	$171.95	10.806%	$190.5309	$190.53	$190.55	$190.50
Purchase #5	$167.37	11.197%	$186.1104	$186.11	$186.10	$186.10
Purchase #6	$31.63	5.152%	$33.2596	$33.26	$33.25	$33.30
Purchase #7	$234.70	12.838%	$264.8308	$264.83	$264.85	$264.80
7 purchase totals =	$1,091.55		$1,217.4799	$1,217.48	$1,217.55	$1,217.50