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	$246.65	13.829%	$280.7592	$280.76	$280.75	$280.80
Purchase #2	$182.98	9.746%	$200.8132	$200.81	$200.80	$200.80
Purchase #3	$13.86	9.810%	$15.2197	$15.22	$15.20	$15.20
Purchase #4	$153.54	10.738%	$170.0271	$170.03	$170.05	$170.00
Purchase #5	$160.52	3.268%	$165.7658	$165.77	$165.75	$165.80
Purchase #6	$11.31	13.431%	$12.829	$12.83	$12.85	$12.80
Purchase #7	$192.61	11.693%	$215.1319	$215.13	$215.15	$215.10
7 purchase totals =	$961.47		$1,060.5459	$1,060.55	$1,060.55	$1,060.50