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	$48.66	11.283%	$54.1503	$54.15	$54.15	$54.20
Purchase #2	$65.28	9.519%	$71.494	$71.49	$71.50	$71.50
Purchase #3	$169.90	12.568%	$191.253	$191.25	$191.25	$191.30
Purchase #4	$182.50	13.218%	$206.6229	$206.62	$206.60	$206.60
Purchase #5	$248.56	4.215%	$259.0368	$259.04	$259.05	$259.00
Purchase #6	$34.89	9.714%	$38.2792	$38.28	$38.30	$38.30
Purchase #7	$42.51	11.743%	$47.5019	$47.50	$47.50	$47.50
7 purchase totals =	$792.30		$868.3381	$868.33	$868.35	$868.40