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	$243.92	11.639%	$272.3098	$272.31	$272.30	$272.30
Purchase #2	$187.48	11.175%	$208.4309	$208.43	$208.45	$208.40
Purchase #3	$182.43	5.191%	$191.8999	$191.90	$191.90	$191.90
Purchase #4	$231.87	9.730%	$254.431	$254.43	$254.45	$254.40
Purchase #5	$223.46	12.124%	$250.5523	$250.55	$250.55	$250.60
Purchase #6	$39.60	7.600%	$42.6096	$42.61	$42.60	$42.60
Purchase #7	$208.75	11.118%	$231.9588	$231.96	$231.95	$232.00
7 purchase totals =	$1,317.51		$1,452.1923	$1,452.19	$1,452.20	$1,452.20