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	$151.41	12.827%	$170.8314	$170.83	$170.85	$170.80
Purchase #2	$164.40	4.647%	$172.0397	$172.04	$172.05	$172.00
Purchase #3	$105.31	7.745%	$113.4663	$113.47	$113.45	$113.50
Purchase #4	$79.88	12.813%	$90.115	$90.12	$90.10	$90.10
Purchase #5	$167.51	4.529%	$175.0965	$175.10	$175.10	$175.10
Purchase #6	$81.59	4.855%	$85.5512	$85.55	$85.55	$85.60
Purchase #7	$129.91	5.146%	$136.5952	$136.60	$136.60	$136.60
7 purchase totals =	$880.01		$943.6953	$943.71	$943.70	$943.70