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	$168.42	13.449%	$191.0708	$191.07	$191.05	$191.10
Purchase #2	$136.55	4.746%	$143.0307	$143.03	$143.05	$143.00
Purchase #3	$125.72	9.297%	$137.4082	$137.41	$137.40	$137.40
Purchase #4	$71.53	6.407%	$76.1129	$76.11	$76.10	$76.10
Purchase #5	$36.53	6.628%	$38.9512	$38.95	$38.95	$39.00
Purchase #6	$90.81	3.669%	$94.1418	$94.14	$94.15	$94.10
Purchase #7	$171.74	11.131%	$190.8564	$190.86	$190.85	$190.90
7 purchase totals =	$801.30		$871.5720	$871.57	$871.55	$871.60