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	$23.56	5.438%	$24.8412	$24.84	$24.85	$24.80
Purchase #2	$78.42	4.431%	$81.8948	$81.89	$81.90	$81.90
Purchase #3	$42.29	5.244%	$44.5077	$44.51	$44.50	$44.50
Purchase #4	$191.35	10.587%	$211.6082	$211.61	$211.60	$211.60
Purchase #5	$114.37	3.435%	$118.2986	$118.30	$118.30	$118.30
Purchase #6	$216.87	13.703%	$246.5877	$246.59	$246.60	$246.60
Purchase #7	$64.87	10.734%	$71.8331	$71.83	$71.85	$71.80
7 purchase totals =	$731.73		$799.5713	$799.57	$799.60	$799.50