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	$209.33	6.566%	$223.0746	$223.07	$223.05	$223.10
Purchase #2	$157.30	12.250%	$176.5693	$176.57	$176.55	$176.60
Purchase #3	$151.84	5.262%	$159.8298	$159.83	$159.85	$159.80
Purchase #4	$9.77	8.598%	$10.61	$10.61	$10.60	$10.60
Purchase #5	$172.92	7.156%	$185.2942	$185.29	$185.30	$185.30
Purchase #6	$154.51	6.507%	$164.564	$164.56	$164.55	$164.60
Purchase #7	$241.37	3.562%	$249.9676	$249.97	$249.95	$250.00
7 purchase totals =	$1,097.04		$1,169.9095	$1,169.90	$1,169.85	$1,170.00