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	$158.25	6.528%	$168.5806	$168.58	$168.60	$168.60
Purchase #2	$5.52	9.476%	$6.0431	$6.04	$6.05	$6.00
Purchase #3	$79.75	13.570%	$90.5721	$90.57	$90.55	$90.60
Purchase #4	$75.85	13.157%	$85.8296	$85.83	$85.85	$85.80
Purchase #5	$228.90	11.811%	$255.9354	$255.94	$255.95	$255.90
Purchase #6	$147.70	13.516%	$167.6631	$167.66	$167.65	$167.70
Purchase #7	$35.39	5.166%	$37.2182	$37.22	$37.20	$37.20
7 purchase totals =	$731.36		$811.8421	$811.84	$811.85	$811.80