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	$43.54	5.226%	$45.8154	$45.82	$45.80	$45.80
Purchase #2	$177.94	10.688%	$196.9582	$196.96	$196.95	$197.00
Purchase #3	$246.91	9.110%	$269.4035	$269.40	$269.40	$269.40
Purchase #4	$184.56	6.369%	$196.3146	$196.31	$196.30	$196.30
Purchase #5	$58.73	9.504%	$64.3117	$64.31	$64.30	$64.30
Purchase #6	$152.99	8.117%	$165.4082	$165.41	$165.40	$165.40
Purchase #7	$193.27	7.766%	$208.2793	$208.28	$208.30	$208.30
7 purchase totals =	$1,057.94		$1,146.4909	$1,146.49	$1,146.45	$1,146.50