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	$189.98	8.113%	$205.3931	$205.39	$205.40	$205.40
Purchase #2	$69.59	5.490%	$73.4105	$73.41	$73.40	$73.40
Purchase #3	$63.48	12.848%	$71.6359	$71.64	$71.65	$71.60
Purchase #4	$247.54	12.761%	$279.1286	$279.13	$279.15	$279.10
Purchase #5	$64.91	10.531%	$71.7457	$71.75	$71.75	$71.70
Purchase #6	$249.45	8.760%	$271.3018	$271.30	$271.30	$271.30
Purchase #7	$150.39	5.833%	$159.1622	$159.16	$159.15	$159.20
7 purchase totals =	$1,035.34		$1,131.7778	$1,131.78	$1,131.80	$1,131.70