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	$58.53	6.809%	$62.5153	$62.52	$62.50	$62.50
Purchase #2	$13.48	13.530%	$15.3038	$15.30	$15.30	$15.30
Purchase #3	$83.58	7.838%	$90.131	$90.13	$90.15	$90.10
Purchase #4	$82.70	6.431%	$88.0184	$88.02	$88.00	$88.00
Purchase #5	$174.52	9.567%	$191.2163	$191.22	$191.20	$191.20
Purchase #6	$80.95	3.331%	$83.6464	$83.65	$83.65	$83.60
Purchase #7	$126.40	4.742%	$132.3939	$132.39	$132.40	$132.40
7 purchase totals =	$620.16		$663.2251	$663.23	$663.20	$663.10