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	$158.41	6.119%	$168.1031	$168.10	$168.10	$168.10
Purchase #2	$174.56	3.629%	$180.8948	$180.89	$180.90	$180.90
Purchase #3	$10.77	12.763%	$12.1446	$12.14	$12.15	$12.10
Purchase #4	$148.39	5.754%	$156.9284	$156.93	$156.95	$156.90
Purchase #5	$68.94	4.517%	$72.054	$72.05	$72.05	$72.10
Purchase #6	$149.42	12.578%	$168.214	$168.21	$168.20	$168.20
Purchase #7	$130.87	5.402%	$137.9396	$137.94	$137.95	$137.90
7 purchase totals =	$841.36		$896.2785	$896.26	$896.30	$896.20