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	$37.58	8.435%	$40.7499	$40.75	$40.75	$40.70
Purchase #2	$207.78	4.318%	$216.7519	$216.75	$216.75	$216.80
Purchase #3	$56.76	4.862%	$59.5197	$59.52	$59.50	$59.50
Purchase #4	$164.37	6.487%	$175.0327	$175.03	$175.05	$175.00
Purchase #5	$46.45	12.138%	$52.0881	$52.09	$52.10	$52.10
Purchase #6	$148.42	12.742%	$167.3317	$167.33	$167.35	$167.30
Purchase #7	$137.69	11.540%	$153.5794	$153.58	$153.60	$153.60
7 purchase totals =	$799.05		$865.0534	$865.05	$865.10	$865.00