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	$88.84	6.323%	$94.4574	$94.46	$94.45	$94.50
Purchase #2	$136.49	11.259%	$151.8574	$151.86	$151.85	$151.90
Purchase #3	$95.83	8.406%	$103.8855	$103.89	$103.90	$103.90
Purchase #4	$238.41	13.539%	$270.6883	$270.69	$270.70	$270.70
Purchase #5	$173.50	13.248%	$196.4853	$196.49	$196.50	$196.50
Purchase #6	$58.53	5.794%	$61.9212	$61.92	$61.90	$61.90
Purchase #7	$116.79	10.157%	$128.6524	$128.65	$128.65	$128.70
7 purchase totals =	$908.39		$1,007.9475	$1,007.96	$1,007.95	$1,008.10