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	$137.51	10.769%	$152.3185	$152.32	$152.30	$152.30
Purchase #2	$202.44	11.438%	$225.5951	$225.60	$225.60	$225.60
Purchase #3	$76.49	13.872%	$87.1007	$87.10	$87.10	$87.10
Purchase #4	$147.33	4.165%	$153.4663	$153.47	$153.45	$153.50
Purchase #5	$79.62	3.813%	$82.6559	$82.66	$82.65	$82.70
Purchase #6	$17.67	13.771%	$20.1033	$20.10	$20.10	$20.10
Purchase #7	$212.64	4.543%	$222.3002	$222.30	$222.30	$222.30
7 purchase totals =	$873.70		$943.5400	$943.55	$943.50	$943.60