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	$216.63	8.872%	$235.8494	$235.85	$235.85	$235.80
Purchase #2	$208.45	7.442%	$223.9628	$223.96	$223.95	$224.00
Purchase #3	$73.63	13.663%	$83.6901	$83.69	$83.70	$83.70
Purchase #4	$15.31	11.109%	$17.0108	$17.01	$17.00	$17.00
Purchase #5	$178.61	5.544%	$188.5121	$188.51	$188.50	$188.50
Purchase #6	$54.72	3.130%	$56.4327	$56.43	$56.45	$56.40
Purchase #7	$144.89	12.198%	$162.5637	$162.56	$162.55	$162.60
7 purchase totals =	$892.24		$968.0216	$968.01	$968.00	$968.00