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	$140.91	9.770%	$154.6769	$154.68	$154.70	$154.70
Purchase #2	$216.69	13.157%	$245.1999	$245.20	$245.20	$245.20
Purchase #3	$75.64	13.414%	$85.7863	$85.79	$85.80	$85.80
Purchase #4	$194.72	11.232%	$216.591	$216.59	$216.60	$216.60
Purchase #5	$112.90	10.325%	$124.5569	$124.56	$124.55	$124.60
Purchase #6	$52.86	13.375%	$59.93	$59.93	$59.95	$59.90
Purchase #7	$151.51	11.784%	$169.3639	$169.36	$169.35	$169.40
7 purchase totals =	$945.23		$1,056.1049	$1,056.11	$1,056.15	$1,056.20