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	$200.43	9.518%	$219.5069	$219.51	$219.50	$219.50
Purchase #2	$171.64	8.605%	$186.4096	$186.41	$186.40	$186.40
Purchase #3	$10.62	6.596%	$11.3205	$11.32	$11.30	$11.30
Purchase #4	$187.59	12.222%	$210.5172	$210.52	$210.50	$210.50
Purchase #5	$40.30	6.381%	$42.8715	$42.87	$42.85	$42.90
Purchase #6	$86.66	5.640%	$91.5476	$91.55	$91.55	$91.50
Purchase #7	$140.39	7.842%	$151.3994	$151.40	$151.40	$151.40
7 purchase totals =	$837.63		$913.5727	$913.58	$913.50	$913.50