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	$96.71	5.691%	$102.2138	$102.21	$102.20	$102.20
Purchase #2	$194.89	5.727%	$206.0514	$206.05	$206.05	$206.10
Purchase #3	$127.86	12.797%	$144.2222	$144.22	$144.20	$144.20
Purchase #4	$37.79	13.562%	$42.9151	$42.92	$42.90	$42.90
Purchase #5	$89.88	4.843%	$94.2329	$94.23	$94.25	$94.20
Purchase #6	$156.59	3.764%	$162.484	$162.48	$162.50	$162.50
Purchase #7	$160.34	10.142%	$176.6017	$176.60	$176.60	$176.60
7 purchase totals =	$864.06		$928.7211	$928.71	$928.70	$928.70