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	$53.86	13.588%	$61.1785	$61.18	$61.20	$61.20
Purchase #2	$237.39	6.783%	$253.4922	$253.49	$253.50	$253.50
Purchase #3	$87.56	7.871%	$94.4518	$94.45	$94.45	$94.50
Purchase #4	$196.61	11.700%	$219.6134	$219.61	$219.60	$219.60
Purchase #5	$102.42	6.326%	$108.8991	$108.90	$108.90	$108.90
Purchase #6	$156.36	5.745%	$165.3429	$165.34	$165.35	$165.30
Purchase #7	$156.48	7.831%	$168.7339	$168.73	$168.75	$168.70
7 purchase totals =	$990.68		$1,071.7118	$1,071.70	$1,071.75	$1,071.70