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	$104.43	7.141%	$111.8873	$111.89	$111.90	$111.90
Purchase #2	$65.71	9.739%	$72.1095	$72.11	$72.10	$72.10
Purchase #3	$106.42	11.532%	$118.6924	$118.69	$118.70	$118.70
Purchase #4	$203.53	7.106%	$217.9928	$217.99	$218.00	$218.00
Purchase #5	$228.67	5.408%	$241.0365	$241.04	$241.05	$241.00
Purchase #6	$83.42	8.296%	$90.3405	$90.34	$90.35	$90.30
Purchase #7	$82.68	9.163%	$90.256	$90.26	$90.25	$90.30
7 purchase totals =	$874.86		$942.3150	$942.32	$942.35	$942.30