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	$229.63	7.673%	$247.2495	$247.25	$247.25	$247.20
Purchase #2	$234.56	8.342%	$254.127	$254.13	$254.15	$254.10
Purchase #3	$125.99	12.585%	$141.8458	$141.85	$141.85	$141.80
Purchase #4	$199.43	11.528%	$222.4203	$222.42	$222.40	$222.40
Purchase #5	$47.82	12.550%	$53.8214	$53.82	$53.80	$53.80
Purchase #6	$57.25	10.843%	$63.4576	$63.46	$63.45	$63.50
Purchase #7	$245.54	13.676%	$279.1201	$279.12	$279.10	$279.10
7 purchase totals =	$1,140.22		$1,262.0417	$1,262.05	$1,262.00	$1,261.90