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	$149.56	7.688%	$161.0582	$161.06	$161.05	$161.10
Purchase #2	$147.86	13.385%	$167.6511	$167.65	$167.65	$167.70
Purchase #3	$87.48	5.754%	$92.5136	$92.51	$92.50	$92.50
Purchase #4	$82.79	6.351%	$88.048	$88.05	$88.05	$88.00
Purchase #5	$67.33	8.246%	$72.882	$72.88	$72.90	$72.90
Purchase #6	$213.46	11.838%	$238.7294	$238.73	$238.75	$238.70
Purchase #7	$90.38	6.320%	$96.092	$96.09	$96.10	$96.10
7 purchase totals =	$838.86		$916.9743	$916.97	$917.00	$917.00