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	$33.53	12.502%	$37.7219	$37.72	$37.70	$37.70
Purchase #2	$33.56	12.644%	$37.8033	$37.80	$37.80	$37.80
Purchase #3	$19.62	11.358%	$21.8484	$21.85	$21.85	$21.80
Purchase #4	$226.30	11.712%	$252.8043	$252.80	$252.80	$252.80
Purchase #5	$119.76	10.179%	$131.9504	$131.95	$131.95	$132.00
Purchase #6	$101.46	10.546%	$112.16	$112.16	$112.15	$112.20
Purchase #7	$77.93	13.332%	$88.3196	$88.32	$88.30	$88.30
7 purchase totals =	$612.16		$682.6079	$682.60	$682.55	$682.60