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	$172.29	11.701%	$192.4497	$192.45	$192.45	$192.40
Purchase #2	$163.71	4.615%	$171.2652	$171.27	$171.25	$171.30
Purchase #3	$78.69	3.540%	$81.4756	$81.48	$81.50	$81.50
Purchase #4	$40.69	12.457%	$45.7588	$45.76	$45.75	$45.80
Purchase #5	$142.63	12.810%	$160.9009	$160.90	$160.90	$160.90
Purchase #6	$71.58	8.819%	$77.8926	$77.89	$77.90	$77.90
Purchase #7	$53.81	4.530%	$56.2476	$56.25	$56.25	$56.20
7 purchase totals =	$723.40		$785.9904	$786.00	$786.00	$786.00