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	$209.69	7.587%	$225.5992	$225.60	$225.60	$225.60
Purchase #2	$136.80	7.319%	$146.8124	$146.81	$146.80	$146.80
Purchase #3	$229.33	7.842%	$247.3141	$247.31	$247.30	$247.30
Purchase #4	$221.54	12.620%	$249.4983	$249.50	$249.50	$249.50
Purchase #5	$241.42	8.167%	$261.1368	$261.14	$261.15	$261.10
Purchase #6	$88.91	11.871%	$99.4645	$99.46	$99.45	$99.50
Purchase #7	$206.64	9.767%	$226.8225	$226.82	$226.80	$226.80
7 purchase totals =	$1,334.33		$1,456.6478	$1,456.64	$1,456.60	$1,456.60