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	$246.83	7.253%	$264.7326	$264.73	$264.75	$264.70
Purchase #2	$61.79	7.338%	$66.3242	$66.32	$66.30	$66.30
Purchase #3	$9.91	3.218%	$10.2289	$10.23	$10.25	$10.20
Purchase #4	$146.99	10.491%	$162.4107	$162.41	$162.40	$162.40
Purchase #5	$78.77	11.548%	$87.8664	$87.87	$87.85	$87.90
Purchase #6	$233.94	4.215%	$243.8006	$243.80	$243.80	$243.80
Purchase #7	$203.65	9.276%	$222.5406	$222.54	$222.55	$222.50
7 purchase totals =	$981.88		$1,057.9040	$1,057.90	$1,057.90	$1,057.80