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	$133.42	9.247%	$145.7573	$145.76	$145.75	$145.80
Purchase #2	$191.82	4.785%	$200.9986	$201.00	$201.00	$201.00
Purchase #3	$89.68	12.425%	$100.8227	$100.82	$100.80	$100.80
Purchase #4	$43.88	10.526%	$48.4988	$48.50	$48.50	$48.50
Purchase #5	$56.83	5.468%	$59.9375	$59.94	$59.95	$59.90
Purchase #6	$64.45	10.236%	$71.0471	$71.05	$71.05	$71.00
Purchase #7	$40.86	5.411%	$43.0709	$43.07	$43.05	$43.10
7 purchase totals =	$620.94		$670.1329	$670.14	$670.10	$670.10