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	$43.32	7.363%	$46.5097	$46.51	$46.50	$46.50
Purchase #2	$231.30	9.429%	$253.1093	$253.11	$253.10	$253.10
Purchase #3	$9.57	6.458%	$10.188	$10.19	$10.20	$10.20
Purchase #4	$36.51	12.362%	$41.0234	$41.02	$41.00	$41.00
Purchase #5	$102.68	8.803%	$111.7189	$111.72	$111.70	$111.70
Purchase #6	$161.51	4.828%	$169.3077	$169.31	$169.30	$169.30
Purchase #7	$103.87	5.506%	$109.5891	$109.59	$109.60	$109.60
7 purchase totals =	$688.76		$741.4461	$741.45	$741.40	$741.40