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	$151.27	10.199%	$166.698	$166.70	$166.70	$166.70
Purchase #2	$147.39	13.684%	$167.5588	$167.56	$167.55	$167.60
Purchase #3	$221.28	11.399%	$246.5037	$246.50	$246.50	$246.50
Purchase #4	$234.32	6.754%	$250.146	$250.15	$250.15	$250.10
Purchase #5	$71.68	8.830%	$78.0093	$78.01	$78.00	$78.00
Purchase #6	$204.40	7.854%	$220.4536	$220.45	$220.45	$220.50
Purchase #7	$123.28	13.664%	$140.125	$140.13	$140.15	$140.10
7 purchase totals =	$1,153.62		$1,269.4944	$1,269.50	$1,269.50	$1,269.50