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	$20.81	12.223%	$23.3536	$23.35	$23.35	$23.40
Purchase #2	$62.87	11.414%	$70.046	$70.05	$70.05	$70.00
Purchase #3	$34.26	10.490%	$37.8539	$37.85	$37.85	$37.90
Purchase #4	$142.59	4.225%	$148.6144	$148.61	$148.60	$148.60
Purchase #5	$92.62	7.372%	$99.4479	$99.45	$99.45	$99.40
Purchase #6	$20.69	8.854%	$22.5219	$22.52	$22.50	$22.50
Purchase #7	$57.83	12.203%	$64.887	$64.89	$64.90	$64.90
7 purchase totals =	$431.67		$466.7247	$466.72	$466.70	$466.70