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	$45.56	11.351%	$50.7315	$50.73	$50.75	$50.70
Purchase #2	$36.68	5.405%	$38.6626	$38.66	$38.65	$38.70
Purchase #3	$229.75	5.723%	$242.8986	$242.90	$242.90	$242.90
Purchase #4	$169.46	5.702%	$179.1226	$179.12	$179.10	$179.10
Purchase #5	$130.85	13.327%	$148.2884	$148.29	$148.30	$148.30
Purchase #6	$104.90	9.304%	$114.6599	$114.66	$114.65	$114.70
Purchase #7	$152.38	13.186%	$172.4728	$172.47	$172.45	$172.50
7 purchase totals =	$869.58		$946.8364	$946.83	$946.80	$946.90