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	$29.33	13.301%	$33.2312	$33.23	$33.25	$33.20
Purchase #2	$175.67	7.279%	$188.457	$188.46	$188.45	$188.50
Purchase #3	$228.94	12.388%	$257.3011	$257.30	$257.30	$257.30
Purchase #4	$152.55	8.745%	$165.8905	$165.89	$165.90	$165.90
Purchase #5	$150.88	9.837%	$165.7221	$165.72	$165.70	$165.70
Purchase #6	$6.77	5.159%	$7.1193	$7.12	$7.10	$7.10
Purchase #7	$119.72	9.709%	$131.3436	$131.34	$131.35	$131.30
7 purchase totals =	$863.86		$949.0648	$949.06	$949.05	$949.00