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	$160.89	7.578%	$173.0822	$173.08	$173.10	$173.10
Purchase #2	$31.49	3.234%	$32.5084	$32.51	$32.50	$32.50
Purchase #3	$202.56	4.517%	$211.7096	$211.71	$211.70	$211.70
Purchase #4	$73.98	7.650%	$79.6395	$79.64	$79.65	$79.60
Purchase #5	$205.76	8.116%	$222.4595	$222.46	$222.45	$222.50
Purchase #6	$243.90	4.604%	$255.1292	$255.13	$255.15	$255.10
Purchase #7	$230.82	8.717%	$250.9406	$250.94	$250.95	$250.90
7 purchase totals =	$1,149.40		$1,225.4690	$1,225.47	$1,225.50	$1,225.40