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	$49.28	12.272%	$55.3276	$55.33	$55.35	$55.30
Purchase #2	$83.79	7.471%	$90.05	$90.05	$90.05	$90.10
Purchase #3	$97.47	4.603%	$101.9565	$101.96	$101.95	$102.00
Purchase #4	$248.98	3.696%	$258.1823	$258.18	$258.20	$258.20
Purchase #5	$89.90	10.344%	$99.1993	$99.20	$99.20	$99.20
Purchase #6	$138.45	4.284%	$144.3812	$144.38	$144.40	$144.40
Purchase #7	$146.57	4.240%	$152.7846	$152.78	$152.80	$152.80
7 purchase totals =	$854.44		$901.8815	$901.88	$901.95	$902.00