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	$26.95	4.361%	$28.1253	$28.13	$28.15	$28.10
Purchase #2	$111.45	12.497%	$125.3779	$125.38	$125.40	$125.40
Purchase #3	$25.76	7.768%	$27.761	$27.76	$27.75	$27.80
Purchase #4	$136.83	10.299%	$150.9221	$150.92	$150.90	$150.90
Purchase #5	$85.76	11.116%	$95.2931	$95.29	$95.30	$95.30
Purchase #6	$33.48	10.832%	$37.1066	$37.11	$37.10	$37.10
Purchase #7	$141.53	13.715%	$160.9408	$160.94	$160.95	$160.90
7 purchase totals =	$561.76		$625.5268	$625.53	$625.55	$625.50