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	$60.56	8.510%	$65.7137	$65.71	$65.70	$65.70
Purchase #2	$237.86	13.567%	$270.1305	$270.13	$270.15	$270.10
Purchase #3	$87.58	11.188%	$97.3785	$97.38	$97.40	$97.40
Purchase #4	$229.37	13.145%	$259.5207	$259.52	$259.50	$259.50
Purchase #5	$43.56	5.347%	$45.8892	$45.89	$45.90	$45.90
Purchase #6	$219.61	6.296%	$233.4366	$233.44	$233.45	$233.40
Purchase #7	$240.76	5.463%	$253.9127	$253.91	$253.90	$253.90
7 purchase totals =	$1,119.30		$1,225.9819	$1,225.98	$1,226.00	$1,225.90