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	$173.98	3.708%	$180.4312	$180.43	$180.45	$180.40
Purchase #2	$185.37	7.298%	$198.8983	$198.90	$198.90	$198.90
Purchase #3	$149.36	3.698%	$154.8833	$154.88	$154.90	$154.90
Purchase #4	$56.94	7.281%	$61.0858	$61.09	$61.10	$61.10
Purchase #5	$28.40	13.725%	$32.2979	$32.30	$32.30	$32.30
Purchase #6	$72.73	5.180%	$76.4974	$76.50	$76.50	$76.50
Purchase #7	$234.91	3.778%	$243.7849	$243.78	$243.80	$243.80
7 purchase totals =	$901.69		$947.8788	$947.88	$947.95	$947.90