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	$212.79	10.484%	$235.0989	$235.10	$235.10	$235.10
Purchase #2	$185.53	9.620%	$203.378	$203.38	$203.40	$203.40
Purchase #3	$200.70	13.275%	$227.3429	$227.34	$227.35	$227.30
Purchase #4	$145.50	13.768%	$165.5324	$165.53	$165.55	$165.50
Purchase #5	$178.32	10.307%	$196.6994	$196.70	$196.70	$196.70
Purchase #6	$64.30	12.531%	$72.3574	$72.36	$72.35	$72.40
Purchase #7	$245.78	11.543%	$274.1504	$274.15	$274.15	$274.20
7 purchase totals =	$1,232.92		$1,374.5594	$1,374.56	$1,374.60	$1,374.60