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	$233.53	3.125%	$240.8278	$240.83	$240.85	$240.80
Purchase #2	$242.47	12.689%	$273.237	$273.24	$273.25	$273.20
Purchase #3	$15.70	11.762%	$17.5466	$17.55	$17.55	$17.50
Purchase #4	$85.56	3.382%	$88.4536	$88.45	$88.45	$88.50
Purchase #5	$48.85	10.206%	$53.8356	$53.84	$53.85	$53.80
Purchase #6	$69.73	9.410%	$76.2916	$76.29	$76.30	$76.30
Purchase #7	$43.58	5.206%	$45.8488	$45.85	$45.85	$45.80
7 purchase totals =	$739.42		$796.0410	$796.05	$796.10	$795.90