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	$67.50	6.282%	$71.7404	$71.74	$71.75	$71.70
Purchase #2	$69.92	12.731%	$78.8215	$78.82	$78.80	$78.80
Purchase #3	$74.68	13.580%	$84.8215	$84.82	$84.80	$84.80
Purchase #4	$144.83	10.361%	$159.8358	$159.84	$159.85	$159.80
Purchase #5	$177.64	6.119%	$188.5098	$188.51	$188.50	$188.50
Purchase #6	$71.71	6.186%	$76.146	$76.15	$76.15	$76.10
Purchase #7	$80.70	10.603%	$89.2566	$89.26	$89.25	$89.30
7 purchase totals =	$686.98		$749.1316	$749.14	$749.10	$749.00