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	$143.96	5.412%	$151.7511	$151.75	$151.75	$151.80
Purchase #2	$161.32	12.207%	$181.0123	$181.01	$181.00	$181.00
Purchase #3	$30.72	3.103%	$31.6732	$31.67	$31.65	$31.70
Purchase #4	$20.34	5.644%	$21.488	$21.49	$21.50	$21.50
Purchase #5	$174.45	3.491%	$180.54	$180.54	$180.55	$180.50
Purchase #6	$32.65	13.744%	$37.1374	$37.14	$37.15	$37.10
Purchase #7	$55.89	6.221%	$59.3669	$59.37	$59.35	$59.40
7 purchase totals =	$619.33		$662.9689	$662.97	$662.95	$663.00