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	$76.91	11.355%	$85.6431	$85.64	$85.65	$85.60
Purchase #2	$81.57	9.188%	$89.0647	$89.06	$89.05	$89.10
Purchase #3	$105.90	5.709%	$111.9458	$111.95	$111.95	$111.90
Purchase #4	$152.68	8.859%	$166.2059	$166.21	$166.20	$166.20
Purchase #5	$124.67	12.212%	$139.8947	$139.89	$139.90	$139.90
Purchase #6	$103.47	3.373%	$106.96	$106.96	$106.95	$107.00
Purchase #7	$175.41	11.299%	$195.2296	$195.23	$195.25	$195.20
7 purchase totals =	$820.61		$894.9438	$894.94	$894.95	$894.90