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	$168.48	10.219%	$185.697	$185.70	$185.70	$185.70
Purchase #2	$201.75	11.472%	$224.8948	$224.89	$224.90	$224.90
Purchase #3	$199.79	9.409%	$218.5882	$218.59	$218.60	$218.60
Purchase #4	$79.73	13.820%	$90.7487	$90.75	$90.75	$90.70
Purchase #5	$36.50	12.240%	$40.9676	$40.97	$40.95	$41.00
Purchase #6	$26.49	11.422%	$29.5157	$29.52	$29.50	$29.50
Purchase #7	$137.64	3.168%	$142.0004	$142.00	$142.00	$142.00
7 purchase totals =	$850.38		$932.4124	$932.42	$932.40	$932.40