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	$233.86	10.860%	$259.2572	$259.26	$259.25	$259.30
Purchase #2	$140.51	8.148%	$151.9588	$151.96	$151.95	$152.00
Purchase #3	$10.38	9.338%	$11.3493	$11.35	$11.35	$11.30
Purchase #4	$79.56	12.379%	$89.4087	$89.41	$89.40	$89.40
Purchase #5	$32.96	5.754%	$34.8565	$34.86	$34.85	$34.90
Purchase #6	$111.63	8.324%	$120.9221	$120.92	$120.90	$120.90
Purchase #7	$76.67	11.812%	$85.7263	$85.73	$85.75	$85.70
7 purchase totals =	$685.57		$753.4789	$753.49	$753.45	$753.50