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	$220.92	7.154%	$236.7246	$236.72	$236.70	$236.70
Purchase #2	$72.78	8.399%	$78.8928	$78.89	$78.90	$78.90
Purchase #3	$138.91	10.614%	$153.6539	$153.65	$153.65	$153.70
Purchase #4	$206.86	12.816%	$233.3712	$233.37	$233.35	$233.40
Purchase #5	$54.34	8.170%	$58.7796	$58.78	$58.80	$58.80
Purchase #6	$173.51	12.840%	$195.7887	$195.79	$195.80	$195.80
Purchase #7	$154.96	7.172%	$166.0737	$166.07	$166.05	$166.10
7 purchase totals =	$1,022.28		$1,123.2845	$1,123.27	$1,123.25	$1,123.40