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	$51.89	5.462%	$54.7242	$54.72	$54.70	$54.70
Purchase #2	$209.61	9.557%	$229.6424	$229.64	$229.65	$229.60
Purchase #3	$46.63	3.452%	$48.2397	$48.24	$48.25	$48.20
Purchase #4	$137.48	11.182%	$152.853	$152.85	$152.85	$152.90
Purchase #5	$173.95	11.252%	$193.5229	$193.52	$193.50	$193.50
Purchase #6	$224.64	11.348%	$250.1321	$250.13	$250.15	$250.10
Purchase #7	$117.61	11.860%	$131.5585	$131.56	$131.55	$131.60
7 purchase totals =	$961.81		$1,060.6728	$1,060.66	$1,060.65	$1,060.60