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	$147.95	3.339%	$152.8901	$152.89	$152.90	$152.90
Purchase #2	$136.80	10.276%	$150.8576	$150.86	$150.85	$150.90
Purchase #3	$94.64	12.749%	$106.7057	$106.71	$106.70	$106.70
Purchase #4	$42.42	6.422%	$45.1442	$45.14	$45.15	$45.10
Purchase #5	$198.59	12.152%	$222.7227	$222.72	$222.70	$222.70
Purchase #6	$52.51	12.386%	$59.0139	$59.01	$59.00	$59.00
Purchase #7	$208.69	5.198%	$219.5377	$219.54	$219.55	$219.50
7 purchase totals =	$881.60		$956.8719	$956.87	$956.85	$956.80