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	$126.74	11.378%	$141.1605	$141.16	$141.15	$141.20
Purchase #2	$167.98	8.808%	$182.7757	$182.78	$182.80	$182.80
Purchase #3	$109.28	11.679%	$122.0428	$122.04	$122.05	$122.00
Purchase #4	$71.78	10.526%	$79.3356	$79.34	$79.35	$79.30
Purchase #5	$53.54	11.149%	$59.5092	$59.51	$59.50	$59.50
Purchase #6	$35.34	3.200%	$36.4709	$36.47	$36.45	$36.50
Purchase #7	$136.78	10.769%	$151.5098	$151.51	$151.50	$151.50
7 purchase totals =	$701.44		$772.8045	$772.81	$772.80	$772.80