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	$88.70	5.211%	$93.3222	$93.32	$93.30	$93.30
Purchase #2	$56.91	5.218%	$59.8796	$59.88	$59.90	$59.90
Purchase #3	$29.59	13.781%	$33.6678	$33.67	$33.65	$33.70
Purchase #4	$40.41	11.869%	$45.2063	$45.21	$45.20	$45.20
Purchase #5	$18.64	11.173%	$20.7226	$20.72	$20.70	$20.70
Purchase #6	$184.58	6.212%	$196.0461	$196.05	$196.05	$196.00
Purchase #7	$28.98	12.130%	$32.4953	$32.50	$32.50	$32.50
7 purchase totals =	$447.81		$481.3399	$481.35	$481.30	$481.30