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	$126.72	3.241%	$130.827	$130.83	$130.85	$130.80
Purchase #2	$144.46	5.359%	$152.2016	$152.20	$152.20	$152.20
Purchase #3	$127.90	11.431%	$142.5202	$142.52	$142.50	$142.50
Purchase #4	$197.62	12.562%	$222.445	$222.45	$222.45	$222.40
Purchase #5	$101.27	10.167%	$111.5661	$111.57	$111.55	$111.60
Purchase #6	$192.53	8.573%	$209.0356	$209.04	$209.05	$209.00
Purchase #7	$241.93	11.228%	$269.0939	$269.09	$269.10	$269.10
7 purchase totals =	$1,132.43		$1,237.6894	$1,237.70	$1,237.70	$1,237.60