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	$231.96	6.447%	$246.9145	$246.91	$246.90	$246.90
Purchase #2	$204.72	9.599%	$224.3711	$224.37	$224.35	$224.40
Purchase #3	$239.46	8.401%	$259.577	$259.58	$259.60	$259.60
Purchase #4	$21.35	12.665%	$24.054	$24.05	$24.05	$24.10
Purchase #5	$39.46	7.184%	$42.2948	$42.29	$42.30	$42.30
Purchase #6	$172.42	7.474%	$185.3067	$185.31	$185.30	$185.30
Purchase #7	$141.61	6.344%	$150.5937	$150.59	$150.60	$150.60
7 purchase totals =	$1,050.98		$1,133.1118	$1,133.10	$1,133.10	$1,133.20