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	$32.45	10.376%	$35.817	$35.82	$35.80	$35.80
Purchase #2	$191.60	7.615%	$206.1903	$206.19	$206.20	$206.20
Purchase #3	$231.79	5.121%	$243.66	$243.66	$243.65	$243.70
Purchase #4	$143.88	4.611%	$150.5143	$150.51	$150.50	$150.50
Purchase #5	$220.48	5.151%	$231.8369	$231.84	$231.85	$231.80
Purchase #6	$127.34	8.810%	$138.5587	$138.56	$138.55	$138.60
Purchase #7	$52.58	5.103%	$55.2632	$55.26	$55.25	$55.30
7 purchase totals =	$1,000.12		$1,061.8404	$1,061.84	$1,061.80	$1,061.90