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	$245.97	11.642%	$274.6058	$274.61	$274.60	$274.60
Purchase #2	$212.29	3.220%	$219.1257	$219.13	$219.15	$219.10
Purchase #3	$40.40	6.500%	$43.026	$43.03	$43.05	$43.00
Purchase #4	$158.38	8.359%	$171.619	$171.62	$171.60	$171.60
Purchase #5	$179.28	3.579%	$185.6964	$185.70	$185.70	$185.70
Purchase #6	$192.88	11.534%	$215.1268	$215.13	$215.15	$215.10
Purchase #7	$42.50	6.574%	$45.294	$45.29	$45.30	$45.30
7 purchase totals =	$1,071.70		$1,154.4937	$1,154.51	$1,154.55	$1,154.40