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	$84.57	7.205%	$90.6633	$90.66	$90.65	$90.70
Purchase #2	$196.77	11.115%	$218.641	$218.64	$218.65	$218.60
Purchase #3	$140.89	6.798%	$150.4677	$150.47	$150.45	$150.50
Purchase #4	$190.80	10.679%	$211.1755	$211.18	$211.20	$211.20
Purchase #5	$50.78	7.105%	$54.3879	$54.39	$54.40	$54.40
Purchase #6	$164.74	6.210%	$174.9704	$174.97	$174.95	$175.00
Purchase #7	$12.73	11.705%	$14.22	$14.22	$14.20	$14.20
7 purchase totals =	$841.28		$914.5258	$914.53	$914.50	$914.60