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	$164.80	6.395%	$175.339	$175.34	$175.35	$175.30
Purchase #2	$216.43	12.198%	$242.8301	$242.83	$242.85	$242.80
Purchase #3	$72.76	7.871%	$78.4869	$78.49	$78.50	$78.50
Purchase #4	$217.73	12.414%	$244.759	$244.76	$244.75	$244.80
Purchase #5	$87.96	10.874%	$97.5248	$97.52	$97.50	$97.50
Purchase #6	$53.92	9.554%	$59.0715	$59.07	$59.05	$59.10
Purchase #7	$186.97	8.793%	$203.4103	$203.41	$203.40	$203.40
7 purchase totals =	$1,000.57		$1,101.4216	$1,101.42	$1,101.40	$1,101.40