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	$221.53	13.112%	$250.577	$250.58	$250.60	$250.60
Purchase #2	$174.50	4.360%	$182.1082	$182.11	$182.10	$182.10
Purchase #3	$181.59	12.105%	$203.5715	$203.57	$203.55	$203.60
Purchase #4	$66.85	13.118%	$75.6194	$75.62	$75.60	$75.60
Purchase #5	$112.92	12.350%	$126.8656	$126.87	$126.85	$126.90
Purchase #6	$67.31	12.184%	$75.5111	$75.51	$75.50	$75.50
Purchase #7	$99.96	11.568%	$111.5234	$111.52	$111.50	$111.50
7 purchase totals =	$924.66		$1,025.7762	$1,025.78	$1,025.70	$1,025.80