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	$148.39	6.403%	$157.8914	$157.89	$157.90	$157.90
Purchase #2	$138.83	4.629%	$145.2564	$145.26	$145.25	$145.30
Purchase #3	$156.94	9.798%	$172.317	$172.32	$172.30	$172.30
Purchase #4	$153.51	4.773%	$160.837	$160.84	$160.85	$160.80
Purchase #5	$37.94	9.415%	$41.5121	$41.51	$41.50	$41.50
Purchase #6	$211.29	12.797%	$238.3288	$238.33	$238.35	$238.30
Purchase #7	$128.96	8.224%	$139.5657	$139.57	$139.55	$139.60
7 purchase totals =	$975.86		$1,055.7084	$1,055.72	$1,055.70	$1,055.70