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	$161.71	9.804%	$177.564	$177.56	$177.55	$177.60
Purchase #2	$233.78	9.866%	$256.8447	$256.84	$256.85	$256.80
Purchase #3	$250.47	4.359%	$261.388	$261.39	$261.40	$261.40
Purchase #4	$180.50	12.810%	$203.6221	$203.62	$203.60	$203.60
Purchase #5	$151.26	12.417%	$170.042	$170.04	$170.05	$170.00
Purchase #6	$190.32	3.169%	$196.3512	$196.35	$196.35	$196.40
Purchase #7	$91.90	7.820%	$99.0866	$99.09	$99.10	$99.10
7 purchase totals =	$1,259.94		$1,364.8986	$1,364.89	$1,364.90	$1,364.90