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	$40.50	12.446%	$45.5406	$45.54	$45.55	$45.50
Purchase #2	$35.46	5.118%	$37.2748	$37.27	$37.25	$37.30
Purchase #3	$193.40	5.143%	$203.3466	$203.35	$203.35	$203.30
Purchase #4	$69.29	13.840%	$78.8797	$78.88	$78.90	$78.90
Purchase #5	$160.65	10.837%	$178.0596	$178.06	$178.05	$178.10
Purchase #6	$213.68	11.110%	$237.4198	$237.42	$237.40	$237.40
Purchase #7	$237.66	10.118%	$261.7064	$261.71	$261.70	$261.70
7 purchase totals =	$950.64		$1,042.2275	$1,042.23	$1,042.20	$1,042.20