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	$192.57	13.811%	$219.1658	$219.17	$219.15	$219.20
Purchase #2	$160.50	13.782%	$182.6201	$182.62	$182.60	$182.60
Purchase #3	$140.31	8.535%	$152.2855	$152.29	$152.30	$152.30
Purchase #4	$221.40	13.539%	$251.3753	$251.38	$251.40	$251.40
Purchase #5	$59.52	4.411%	$62.1454	$62.15	$62.15	$62.10
Purchase #6	$44.42	9.524%	$48.6506	$48.65	$48.65	$48.70
Purchase #7	$185.60	12.206%	$208.2543	$208.25	$208.25	$208.30
7 purchase totals =	$1,004.32		$1,124.4970	$1,124.51	$1,124.50	$1,124.60