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	$242.32	7.527%	$260.5594	$260.56	$260.55	$260.60
Purchase #2	$76.35	3.274%	$78.8497	$78.85	$78.85	$78.80
Purchase #3	$83.61	6.625%	$89.1492	$89.15	$89.15	$89.10
Purchase #4	$241.71	5.450%	$254.8832	$254.88	$254.90	$254.90
Purchase #5	$250.61	11.351%	$279.0567	$279.06	$279.05	$279.10
Purchase #6	$126.90	6.552%	$135.2145	$135.21	$135.20	$135.20
Purchase #7	$167.44	13.558%	$190.1415	$190.14	$190.15	$190.10
7 purchase totals =	$1,188.94		$1,287.8542	$1,287.85	$1,287.85	$1,287.80