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	$206.59	7.502%	$222.0884	$222.09	$222.10	$222.10
Purchase #2	$197.33	10.435%	$217.9214	$217.92	$217.90	$217.90
Purchase #3	$79.32	3.572%	$82.1533	$82.15	$82.15	$82.20
Purchase #4	$97.59	8.103%	$105.4977	$105.50	$105.50	$105.50
Purchase #5	$100.57	4.638%	$105.2344	$105.23	$105.25	$105.20
Purchase #6	$97.77	9.229%	$106.7932	$106.79	$106.80	$106.80
Purchase #7	$142.72	10.106%	$157.1433	$157.14	$157.15	$157.10
7 purchase totals =	$921.89		$996.8317	$996.82	$996.85	$996.80