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	$223.72	11.223%	$248.8281	$248.83	$248.85	$248.80
Purchase #2	$193.61	9.828%	$212.638	$212.64	$212.65	$212.60
Purchase #3	$163.61	10.199%	$180.2966	$180.30	$180.30	$180.30
Purchase #4	$36.50	10.375%	$40.2869	$40.29	$40.30	$40.30
Purchase #5	$79.51	10.605%	$87.942	$87.94	$87.95	$87.90
Purchase #6	$242.37	11.494%	$270.228	$270.23	$270.25	$270.20
Purchase #7	$212.54	4.614%	$222.3466	$222.35	$222.35	$222.30
7 purchase totals =	$1,151.86		$1,262.5662	$1,262.58	$1,262.65	$1,262.40