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	$236.92	7.600%	$254.9259	$254.93	$254.95	$254.90
Purchase #2	$176.65	9.337%	$193.1438	$193.14	$193.15	$193.10
Purchase #3	$223.76	6.513%	$238.3335	$238.33	$238.35	$238.30
Purchase #4	$41.53	11.316%	$46.2295	$46.23	$46.25	$46.20
Purchase #5	$230.55	12.542%	$259.4656	$259.47	$259.45	$259.50
Purchase #6	$89.88	6.313%	$95.5541	$95.55	$95.55	$95.60
Purchase #7	$85.31	6.380%	$90.7528	$90.75	$90.75	$90.80
7 purchase totals =	$1,084.60		$1,178.4052	$1,178.40	$1,178.45	$1,178.40