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	$29.28	9.445%	$32.0455	$32.05	$32.05	$32.00
Purchase #2	$6.28	10.846%	$6.9611	$6.96	$6.95	$7.00
Purchase #3	$75.86	10.123%	$83.5393	$83.54	$83.55	$83.50
Purchase #4	$88.34	12.447%	$99.3357	$99.34	$99.35	$99.30
Purchase #5	$74.68	7.481%	$80.2668	$80.27	$80.25	$80.30
Purchase #6	$110.90	4.156%	$115.509	$115.51	$115.50	$115.50
Purchase #7	$137.85	10.704%	$152.6055	$152.61	$152.60	$152.60
7 purchase totals =	$523.19		$570.2629	$570.28	$570.25	$570.20