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	$163.33	13.470%	$185.3306	$185.33	$185.35	$185.30
Purchase #2	$6.70	12.346%	$7.5272	$7.53	$7.55	$7.50
Purchase #3	$191.32	7.171%	$205.0396	$205.04	$205.05	$205.00
Purchase #4	$141.70	12.378%	$159.2396	$159.24	$159.25	$159.20
Purchase #5	$45.49	5.571%	$48.0242	$48.02	$48.00	$48.00
Purchase #6	$250.93	7.527%	$269.8175	$269.82	$269.80	$269.80
Purchase #7	$18.86	8.175%	$20.4018	$20.40	$20.40	$20.40
7 purchase totals =	$818.33		$895.3805	$895.38	$895.40	$895.20