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	$80.26	6.539%	$85.5082	$85.51	$85.50	$85.50
Purchase #2	$166.66	5.561%	$175.928	$175.93	$175.95	$175.90
Purchase #3	$173.96	12.752%	$196.1434	$196.14	$196.15	$196.10
Purchase #4	$83.91	8.130%	$90.7319	$90.73	$90.75	$90.70
Purchase #5	$13.96	8.676%	$15.1712	$15.17	$15.15	$15.20
Purchase #6	$73.53	13.502%	$83.458	$83.46	$83.45	$83.50
Purchase #7	$70.59	4.122%	$73.4997	$73.50	$73.50	$73.50
7 purchase totals =	$662.87		$720.4404	$720.44	$720.45	$720.40