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	$188.67	6.447%	$200.8336	$200.83	$200.85	$200.80
Purchase #2	$50.70	9.580%	$55.5571	$55.56	$55.55	$55.60
Purchase #3	$56.78	4.169%	$59.1472	$59.15	$59.15	$59.10
Purchase #4	$42.80	6.145%	$45.4301	$45.43	$45.45	$45.40
Purchase #5	$199.25	7.319%	$213.8331	$213.83	$213.85	$213.80
Purchase #6	$21.28	5.662%	$22.4849	$22.48	$22.50	$22.50
Purchase #7	$111.93	7.405%	$120.2184	$120.22	$120.20	$120.20
7 purchase totals =	$671.41		$717.5044	$717.50	$717.55	$717.40