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	$215.79	4.478%	$225.4531	$225.45	$225.45	$225.50
Purchase #2	$57.46	9.147%	$62.7159	$62.72	$62.70	$62.70
Purchase #3	$81.89	13.331%	$92.8068	$92.81	$92.80	$92.80
Purchase #4	$161.99	6.721%	$172.8773	$172.88	$172.90	$172.90
Purchase #5	$159.76	6.316%	$169.8504	$169.85	$169.85	$169.90
Purchase #6	$131.44	7.613%	$141.4465	$141.45	$141.45	$141.40
Purchase #7	$59.38	4.616%	$62.121	$62.12	$62.10	$62.10
7 purchase totals =	$867.71		$927.2710	$927.28	$927.25	$927.30