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	$207.41	9.854%	$227.8482	$227.85	$227.85	$227.80
Purchase #2	$214.74	4.255%	$223.8772	$223.88	$223.90	$223.90
Purchase #3	$139.72	8.178%	$151.1463	$151.15	$151.15	$151.10
Purchase #4	$106.37	6.683%	$113.4787	$113.48	$113.50	$113.50
Purchase #5	$44.54	8.603%	$48.3718	$48.37	$48.35	$48.40
Purchase #6	$30.87	9.804%	$33.8965	$33.90	$33.90	$33.90
Purchase #7	$210.71	5.558%	$222.4213	$222.42	$222.40	$222.40
7 purchase totals =	$954.36		$1,021.0400	$1,021.05	$1,021.05	$1,021.00