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	$177.92	6.862%	$190.1289	$190.13	$190.15	$190.10
Purchase #2	$83.31	11.208%	$92.6474	$92.65	$92.65	$92.60
Purchase #3	$31.70	3.476%	$32.8019	$32.80	$32.80	$32.80
Purchase #4	$124.36	10.324%	$137.1989	$137.20	$137.20	$137.20
Purchase #5	$164.51	9.687%	$180.4461	$180.45	$180.45	$180.40
Purchase #6	$163.67	11.419%	$182.3595	$182.36	$182.35	$182.40
Purchase #7	$169.39	12.332%	$190.2792	$190.28	$190.30	$190.30
7 purchase totals =	$914.86		$1,005.8619	$1,005.87	$1,005.90	$1,005.80