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	$48.59	9.217%	$53.0685	$53.07	$53.05	$53.10
Purchase #2	$47.84	5.461%	$50.4525	$50.45	$50.45	$50.50
Purchase #3	$131.62	12.481%	$148.0475	$148.05	$148.05	$148.00
Purchase #4	$6.61	12.174%	$7.4147	$7.41	$7.40	$7.40
Purchase #5	$31.37	13.311%	$35.5457	$35.55	$35.55	$35.50
Purchase #6	$34.83	13.650%	$39.5843	$39.58	$39.60	$39.60
Purchase #7	$129.57	12.627%	$145.9308	$145.93	$145.95	$145.90
7 purchase totals =	$430.43		$480.0440	$480.04	$480.05	$480.00