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	$167.90	5.497%	$177.1295	$177.13	$177.15	$177.10
Purchase #2	$145.60	11.640%	$162.5478	$162.55	$162.55	$162.50
Purchase #3	$6.89	6.313%	$7.325	$7.33	$7.35	$7.30
Purchase #4	$172.64	13.398%	$195.7703	$195.77	$195.75	$195.80
Purchase #5	$131.63	7.183%	$141.085	$141.09	$141.10	$141.10
Purchase #6	$25.96	11.481%	$28.9405	$28.94	$28.95	$28.90
Purchase #7	$105.54	5.637%	$111.4893	$111.49	$111.50	$111.50
7 purchase totals =	$756.16		$824.2874	$824.30	$824.35	$824.20