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	$159.57	13.373%	$180.9093	$180.91	$180.90	$180.90
Purchase #2	$85.37	8.777%	$92.8629	$92.86	$92.85	$92.90
Purchase #3	$55.94	10.844%	$62.0061	$62.01	$62.00	$62.00
Purchase #4	$149.72	7.453%	$160.8786	$160.88	$160.90	$160.90
Purchase #5	$244.86	13.493%	$277.899	$277.90	$277.90	$277.90
Purchase #6	$44.25	11.710%	$49.4317	$49.43	$49.45	$49.40
Purchase #7	$20.54	4.493%	$21.4629	$21.46	$21.45	$21.50
7 purchase totals =	$760.25		$845.4505	$845.45	$845.45	$845.50