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	$211.69	4.110%	$220.3905	$220.39	$220.40	$220.40
Purchase #2	$52.38	5.726%	$55.3793	$55.38	$55.40	$55.40
Purchase #3	$192.72	11.390%	$214.6708	$214.67	$214.65	$214.70
Purchase #4	$59.36	3.735%	$61.5771	$61.58	$61.60	$61.60
Purchase #5	$89.90	11.385%	$100.1351	$100.14	$100.15	$100.10
Purchase #6	$194.39	11.212%	$216.185	$216.19	$216.20	$216.20
Purchase #7	$106.50	6.582%	$113.5098	$113.51	$113.50	$113.50
7 purchase totals =	$906.94		$981.8476	$981.86	$981.90	$981.90