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	$61.83	3.155%	$63.7807	$63.78	$63.80	$63.80
Purchase #2	$249.76	3.318%	$258.047	$258.05	$258.05	$258.00
Purchase #3	$83.64	7.788%	$90.1539	$90.15	$90.15	$90.20
Purchase #4	$26.95	4.407%	$28.1377	$28.14	$28.15	$28.10
Purchase #5	$217.85	3.536%	$225.5532	$225.55	$225.55	$225.60
Purchase #6	$148.58	13.384%	$168.4659	$168.47	$168.45	$168.50
Purchase #7	$185.29	3.102%	$191.0377	$191.04	$191.05	$191.00
7 purchase totals =	$973.90		$1,025.1761	$1,025.18	$1,025.20	$1,025.20