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	$239.76	5.837%	$253.7548	$253.75	$253.75	$253.80
Purchase #2	$96.60	5.414%	$101.8299	$101.83	$101.85	$101.80
Purchase #3	$144.74	6.323%	$153.8919	$153.89	$153.90	$153.90
Purchase #4	$22.97	9.510%	$25.1544	$25.15	$25.15	$25.20
Purchase #5	$96.61	13.142%	$109.3065	$109.31	$109.30	$109.30
Purchase #6	$214.64	3.728%	$222.6418	$222.64	$222.65	$222.60
Purchase #7	$240.81	4.159%	$250.8253	$250.83	$250.85	$250.80
7 purchase totals =	$1,056.13		$1,117.4046	$1,117.40	$1,117.45	$1,117.40