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	$131.75	3.859%	$136.8342	$136.83	$136.85	$136.80
Purchase #2	$56.97	7.377%	$61.1727	$61.17	$61.15	$61.20
Purchase #3	$169.31	12.238%	$190.0302	$190.03	$190.05	$190.00
Purchase #4	$10.53	11.697%	$11.7617	$11.76	$11.75	$11.80
Purchase #5	$215.40	12.497%	$242.3185	$242.32	$242.30	$242.30
Purchase #6	$193.49	8.208%	$209.3717	$209.37	$209.35	$209.40
Purchase #7	$191.86	4.711%	$200.8985	$200.90	$200.90	$200.90
7 purchase totals =	$969.31		$1,052.3875	$1,052.38	$1,052.35	$1,052.40