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	$84.87	10.472%	$93.7576	$93.76	$93.75	$93.80
Purchase #2	$38.65	5.385%	$40.7313	$40.73	$40.75	$40.70
Purchase #3	$185.73	10.148%	$204.5779	$204.58	$204.60	$204.60
Purchase #4	$247.77	10.815%	$274.5663	$274.57	$274.55	$274.60
Purchase #5	$85.31	4.441%	$89.0986	$89.10	$89.10	$89.10
Purchase #6	$82.83	12.796%	$93.4289	$93.43	$93.45	$93.40
Purchase #7	$233.48	13.763%	$265.6139	$265.61	$265.60	$265.60
7 purchase totals =	$958.64		$1,061.7745	$1,061.78	$1,061.80	$1,061.80