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	$59.92	12.676%	$67.5155	$67.52	$67.50	$67.50
Purchase #2	$124.95	12.510%	$140.5812	$140.58	$140.60	$140.60
Purchase #3	$151.75	9.813%	$166.6412	$166.64	$166.65	$166.60
Purchase #4	$81.78	8.468%	$88.7051	$88.71	$88.70	$88.70
Purchase #5	$226.73	3.272%	$234.1486	$234.15	$234.15	$234.10
Purchase #6	$185.87	12.381%	$208.8826	$208.88	$208.90	$208.90
Purchase #7	$37.51	5.241%	$39.4759	$39.48	$39.50	$39.50
7 purchase totals =	$868.51		$945.9501	$945.96	$946.00	$945.90