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	$47.98	13.526%	$54.4698	$54.47	$54.45	$54.50
Purchase #2	$232.36	7.632%	$250.0937	$250.09	$250.10	$250.10
Purchase #3	$135.79	10.548%	$150.1131	$150.11	$150.10	$150.10
Purchase #4	$219.95	8.389%	$238.4016	$238.40	$238.40	$238.40
Purchase #5	$223.41	12.706%	$251.7965	$251.80	$251.80	$251.80
Purchase #6	$145.98	13.313%	$165.4143	$165.41	$165.40	$165.40
Purchase #7	$100.99	11.108%	$112.208	$112.21	$112.20	$112.20
7 purchase totals =	$1,106.46		$1,222.4970	$1,222.49	$1,222.45	$1,222.50