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	$36.54	11.218%	$40.6391	$40.64	$40.65	$40.60
Purchase #2	$143.72	4.369%	$149.9991	$150.00	$150.00	$150.00
Purchase #3	$91.73	5.292%	$96.5844	$96.58	$96.60	$96.60
Purchase #4	$83.26	10.442%	$91.954	$91.95	$91.95	$92.00
Purchase #5	$156.47	10.328%	$172.6302	$172.63	$172.65	$172.60
Purchase #6	$62.42	3.542%	$64.6309	$64.63	$64.65	$64.60
Purchase #7	$125.67	4.340%	$131.1241	$131.12	$131.10	$131.10
7 purchase totals =	$699.81		$747.5618	$747.55	$747.60	$747.50