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	$135.43	9.196%	$147.8841	$147.88	$147.90	$147.90
Purchase #2	$69.59	3.311%	$71.8941	$71.89	$71.90	$71.90
Purchase #3	$65.51	10.137%	$72.1507	$72.15	$72.15	$72.20
Purchase #4	$131.60	11.548%	$146.7972	$146.80	$146.80	$146.80
Purchase #5	$151.80	9.836%	$166.731	$166.73	$166.75	$166.70
Purchase #6	$26.35	9.138%	$28.7579	$28.76	$28.75	$28.80
Purchase #7	$180.93	7.743%	$194.9394	$194.94	$194.95	$194.90
7 purchase totals =	$761.21		$829.1544	$829.15	$829.20	$829.20