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	$204.79	9.129%	$223.4853	$223.49	$223.50	$223.50
Purchase #2	$201.60	4.472%	$210.6156	$210.62	$210.60	$210.60
Purchase #3	$95.47	9.119%	$104.1759	$104.18	$104.20	$104.20
Purchase #4	$149.53	13.315%	$169.4399	$169.44	$169.45	$169.40
Purchase #5	$207.50	9.805%	$227.8454	$227.85	$227.85	$227.80
Purchase #6	$47.60	5.750%	$50.337	$50.34	$50.35	$50.30
Purchase #7	$127.92	7.460%	$137.4628	$137.46	$137.45	$137.50
7 purchase totals =	$1,034.41		$1,123.3619	$1,123.38	$1,123.40	$1,123.30