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	$165.40	13.862%	$188.3277	$188.33	$188.35	$188.30
Purchase #2	$157.30	9.256%	$171.8597	$171.86	$171.85	$171.90
Purchase #3	$161.63	8.808%	$175.8664	$175.87	$175.85	$175.90
Purchase #4	$57.38	3.453%	$59.3613	$59.36	$59.35	$59.40
Purchase #5	$175.49	8.811%	$190.9524	$190.95	$190.95	$191.00
Purchase #6	$105.25	3.434%	$108.8643	$108.86	$108.85	$108.90
Purchase #7	$160.60	6.651%	$171.2815	$171.28	$171.30	$171.30
7 purchase totals =	$983.05		$1,066.5133	$1,066.51	$1,066.50	$1,066.70