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	$177.32	4.525%	$185.3437	$185.34	$185.35	$185.30
Purchase #2	$144.82	7.788%	$156.0986	$156.10	$156.10	$156.10
Purchase #3	$94.36	13.303%	$106.9127	$106.91	$106.90	$106.90
Purchase #4	$28.84	11.146%	$32.0545	$32.05	$32.05	$32.10
Purchase #5	$141.29	3.535%	$146.2846	$146.28	$146.30	$146.30
Purchase #6	$33.63	12.562%	$37.8546	$37.85	$37.85	$37.90
Purchase #7	$234.95	3.406%	$242.9524	$242.95	$242.95	$243.00
7 purchase totals =	$855.21		$907.5011	$907.48	$907.50	$907.60