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	$184.96	11.783%	$206.7538	$206.75	$206.75	$206.80
Purchase #2	$225.88	13.695%	$256.8143	$256.81	$256.80	$256.80
Purchase #3	$35.88	13.864%	$40.8544	$40.85	$40.85	$40.90
Purchase #4	$140.35	4.296%	$146.3794	$146.38	$146.40	$146.40
Purchase #5	$109.40	13.691%	$124.378	$124.38	$124.40	$124.40
Purchase #6	$154.74	7.540%	$166.4074	$166.41	$166.40	$166.40
Purchase #7	$20.44	10.234%	$22.5318	$22.53	$22.55	$22.50
7 purchase totals =	$871.65		$964.1191	$964.11	$964.15	$964.20