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	$74.66	10.698%	$82.6471	$82.65	$82.65	$82.60
Purchase #2	$184.98	6.293%	$196.6208	$196.62	$196.60	$196.60
Purchase #3	$228.87	7.740%	$246.5845	$246.58	$246.60	$246.60
Purchase #4	$120.62	10.171%	$132.8883	$132.89	$132.90	$132.90
Purchase #5	$10.91	12.846%	$12.3115	$12.31	$12.30	$12.30
Purchase #6	$215.93	5.217%	$227.1951	$227.20	$227.20	$227.20
Purchase #7	$119.86	10.502%	$132.4477	$132.45	$132.45	$132.40
7 purchase totals =	$955.83		$1,030.6950	$1,030.70	$1,030.70	$1,030.60