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	$216.85	7.164%	$232.3851	$232.39	$232.40	$232.40
Purchase #2	$74.51	5.625%	$78.7012	$78.70	$78.70	$78.70
Purchase #3	$6.80	8.808%	$7.3989	$7.40	$7.40	$7.40
Purchase #4	$232.96	5.495%	$245.7612	$245.76	$245.75	$245.80
Purchase #5	$139.90	10.201%	$154.1712	$154.17	$154.15	$154.20
Purchase #6	$127.86	11.622%	$142.7199	$142.72	$142.70	$142.70
Purchase #7	$127.62	11.562%	$142.3754	$142.38	$142.40	$142.40
7 purchase totals =	$926.50		$1,003.5129	$1,003.52	$1,003.50	$1,003.60