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	$100.93	10.388%	$111.4146	$111.41	$111.40	$111.40
Purchase #2	$103.46	9.258%	$113.0383	$113.04	$113.05	$113.00
Purchase #3	$245.74	7.518%	$264.2147	$264.21	$264.20	$264.20
Purchase #4	$39.37	3.763%	$40.8515	$40.85	$40.85	$40.90
Purchase #5	$42.85	6.665%	$45.706	$45.71	$45.70	$45.70
Purchase #6	$165.43	7.197%	$177.336	$177.34	$177.35	$177.30
Purchase #7	$118.90	11.836%	$132.973	$132.97	$132.95	$133.00
7 purchase totals =	$816.68		$885.5341	$885.53	$885.50	$885.50