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	$248.96	6.578%	$265.3366	$265.34	$265.35	$265.30
Purchase #2	$64.71	12.578%	$72.8492	$72.85	$72.85	$72.80
Purchase #3	$153.35	7.793%	$165.3006	$165.30	$165.30	$165.30
Purchase #4	$34.92	13.183%	$39.5235	$39.52	$39.50	$39.50
Purchase #5	$135.61	12.318%	$152.3144	$152.31	$152.30	$152.30
Purchase #6	$157.88	13.323%	$178.9144	$178.91	$178.90	$178.90
Purchase #7	$209.94	5.620%	$221.7386	$221.74	$221.75	$221.70
7 purchase totals =	$1,005.37		$1,095.9773	$1,095.97	$1,095.95	$1,095.80