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	$222.91	13.510%	$253.0251	$253.03	$253.05	$253.00
Purchase #2	$48.84	11.379%	$54.3975	$54.40	$54.40	$54.40
Purchase #3	$75.35	13.303%	$85.3738	$85.37	$85.35	$85.40
Purchase #4	$79.89	9.637%	$87.589	$87.59	$87.60	$87.60
Purchase #5	$126.95	13.155%	$143.6503	$143.65	$143.65	$143.70
Purchase #6	$209.52	4.297%	$218.5231	$218.52	$218.50	$218.50
Purchase #7	$35.50	9.424%	$38.8455	$38.85	$38.85	$38.80
7 purchase totals =	$798.96		$881.4043	$881.41	$881.40	$881.40