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	$110.75	11.533%	$123.5228	$123.52	$123.50	$123.50
Purchase #2	$142.89	6.861%	$152.6937	$152.69	$152.70	$152.70
Purchase #3	$57.94	7.138%	$62.0758	$62.08	$62.10	$62.10
Purchase #4	$38.74	5.585%	$40.9036	$40.90	$40.90	$40.90
Purchase #5	$230.41	11.140%	$256.0777	$256.08	$256.10	$256.10
Purchase #6	$21.95	4.287%	$22.891	$22.89	$22.90	$22.90
Purchase #7	$191.30	13.343%	$216.8252	$216.83	$216.85	$216.80
7 purchase totals =	$793.98		$874.9898	$874.99	$875.05	$875.00