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	$143.98	3.412%	$148.8926	$148.89	$148.90	$148.90
Purchase #2	$67.86	8.325%	$73.5093	$73.51	$73.50	$73.50
Purchase #3	$171.55	13.622%	$194.9185	$194.92	$194.90	$194.90
Purchase #4	$52.86	4.246%	$55.1044	$55.10	$55.10	$55.10
Purchase #5	$239.76	13.566%	$272.2858	$272.29	$272.30	$272.30
Purchase #6	$28.43	11.331%	$31.6514	$31.65	$31.65	$31.70
Purchase #7	$49.29	13.499%	$55.9437	$55.94	$55.95	$55.90
7 purchase totals =	$753.73		$832.3057	$832.30	$832.30	$832.30