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	$134.25	7.493%	$144.3094	$144.31	$144.30	$144.30
Purchase #2	$106.73	11.805%	$119.3295	$119.33	$119.35	$119.30
Purchase #3	$247.79	4.320%	$258.4945	$258.49	$258.50	$258.50
Purchase #4	$197.27	12.663%	$222.2503	$222.25	$222.25	$222.30
Purchase #5	$120.33	7.610%	$129.4871	$129.49	$129.50	$129.50
Purchase #6	$231.71	7.738%	$249.6397	$249.64	$249.65	$249.60
Purchase #7	$78.46	8.545%	$85.1644	$85.16	$85.15	$85.20
7 purchase totals =	$1,116.54		$1,208.6749	$1,208.67	$1,208.70	$1,208.70