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	$130.61	12.528%	$146.9728	$146.97	$146.95	$147.00
Purchase #2	$244.25	6.864%	$261.0153	$261.02	$261.00	$261.00
Purchase #3	$52.54	13.329%	$59.5431	$59.54	$59.55	$59.50
Purchase #4	$177.28	8.111%	$191.6592	$191.66	$191.65	$191.70
Purchase #5	$168.59	8.362%	$182.6875	$182.69	$182.70	$182.70
Purchase #6	$175.90	7.514%	$189.1171	$189.12	$189.10	$189.10
Purchase #7	$196.61	13.396%	$222.9479	$222.95	$222.95	$222.90
7 purchase totals =	$1,145.78		$1,253.9429	$1,253.95	$1,253.90	$1,253.90