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	$201.67	11.579%	$225.0214	$225.02	$225.00	$225.00
Purchase #2	$42.49	3.743%	$44.0804	$44.08	$44.10	$44.10
Purchase #3	$177.85	10.661%	$196.8106	$196.81	$196.80	$196.80
Purchase #4	$69.25	9.495%	$75.8253	$75.83	$75.85	$75.80
Purchase #5	$129.48	13.565%	$147.044	$147.04	$147.05	$147.00
Purchase #6	$147.68	5.242%	$155.4214	$155.42	$155.40	$155.40
Purchase #7	$247.48	3.607%	$256.4066	$256.41	$256.40	$256.40
7 purchase totals =	$1,015.90		$1,100.6097	$1,100.61	$1,100.60	$1,100.50