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	$141.77	4.237%	$147.7768	$147.78	$147.80	$147.80
Purchase #2	$144.79	6.864%	$154.7284	$154.73	$154.75	$154.70
Purchase #3	$224.66	11.394%	$250.2578	$250.26	$250.25	$250.30
Purchase #4	$107.39	10.743%	$118.9269	$118.93	$118.95	$118.90
Purchase #5	$191.68	11.730%	$214.1641	$214.16	$214.15	$214.20
Purchase #6	$41.64	10.215%	$45.8935	$45.89	$45.90	$45.90
Purchase #7	$146.27	12.390%	$164.3929	$164.39	$164.40	$164.40
7 purchase totals =	$998.20		$1,096.1404	$1,096.14	$1,096.20	$1,096.20