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	$131.85	11.458%	$146.9574	$146.96	$146.95	$147.00
Purchase #2	$235.66	8.362%	$255.3659	$255.37	$255.35	$255.40
Purchase #3	$160.64	6.398%	$170.9177	$170.92	$170.90	$170.90
Purchase #4	$96.38	4.230%	$100.4569	$100.46	$100.45	$100.50
Purchase #5	$228.80	3.532%	$236.8812	$236.88	$236.90	$236.90
Purchase #6	$44.51	11.502%	$49.6295	$49.63	$49.65	$49.60
Purchase #7	$74.73	10.517%	$82.5894	$82.59	$82.60	$82.60
7 purchase totals =	$972.57		$1,042.7980	$1,042.81	$1,042.80	$1,042.90