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	$132.27	11.763%	$147.8289	$147.83	$147.85	$147.80
Purchase #2	$211.89	10.366%	$233.8545	$233.85	$233.85	$233.90
Purchase #3	$20.48	10.789%	$22.6896	$22.69	$22.70	$22.70
Purchase #4	$7.67	8.817%	$8.3463	$8.35	$8.35	$8.30
Purchase #5	$69.69	12.755%	$78.579	$78.58	$78.60	$78.60
Purchase #6	$35.49	5.180%	$37.3284	$37.33	$37.35	$37.30
Purchase #7	$87.45	11.374%	$97.3966	$97.40	$97.40	$97.40
7 purchase totals =	$564.94		$626.0233	$626.03	$626.10	$626.00