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	$31.25	7.158%	$33.4869	$33.49	$33.50	$33.50
Purchase #2	$12.92	5.766%	$13.665	$13.67	$13.65	$13.70
Purchase #3	$104.45	8.668%	$113.5037	$113.50	$113.50	$113.50
Purchase #4	$171.34	7.471%	$184.1408	$184.14	$184.15	$184.10
Purchase #5	$240.71	7.235%	$258.1254	$258.13	$258.15	$258.10
Purchase #6	$121.90	12.272%	$136.8596	$136.86	$136.85	$136.90
Purchase #7	$59.89	9.802%	$65.7604	$65.76	$65.75	$65.80
7 purchase totals =	$742.46		$805.5418	$805.55	$805.55	$805.60