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	$101.95	11.263%	$113.4326	$113.43	$113.45	$113.40
Purchase #2	$57.75	8.863%	$62.8684	$62.87	$62.85	$62.90
Purchase #3	$77.94	3.272%	$80.4902	$80.49	$80.50	$80.50
Purchase #4	$203.82	4.119%	$212.2153	$212.22	$212.20	$212.20
Purchase #5	$36.74	3.255%	$37.9359	$37.94	$37.95	$37.90
Purchase #6	$110.56	3.525%	$114.4572	$114.46	$114.45	$114.50
Purchase #7	$102.80	13.706%	$116.8898	$116.89	$116.90	$116.90
7 purchase totals =	$691.56		$738.2894	$738.30	$738.30	$738.30