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	$172.90	13.541%	$196.3124	$196.31	$196.30	$196.30
Purchase #2	$191.72	7.610%	$206.3099	$206.31	$206.30	$206.30
Purchase #3	$55.70	3.617%	$57.7147	$57.71	$57.70	$57.70
Purchase #4	$243.84	11.753%	$272.4985	$272.50	$272.50	$272.50
Purchase #5	$207.61	13.871%	$236.4076	$236.41	$236.40	$236.40
Purchase #6	$160.46	7.226%	$172.0548	$172.05	$172.05	$172.10
Purchase #7	$147.50	13.622%	$167.5925	$167.59	$167.60	$167.60
7 purchase totals =	$1,179.73		$1,308.8904	$1,308.88	$1,308.85	$1,308.90