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	$53.75	7.696%	$57.8866	$57.89	$57.90	$57.90
Purchase #2	$202.84	13.327%	$229.8725	$229.87	$229.85	$229.90
Purchase #3	$151.57	13.557%	$172.1183	$172.12	$172.10	$172.10
Purchase #4	$227.48	12.216%	$255.269	$255.27	$255.25	$255.30
Purchase #5	$100.76	12.391%	$113.2452	$113.25	$113.25	$113.20
Purchase #6	$32.68	7.666%	$35.1852	$35.19	$35.20	$35.20
Purchase #7	$175.99	5.474%	$185.6237	$185.62	$185.60	$185.60
7 purchase totals =	$945.07		$1,049.2005	$1,049.21	$1,049.15	$1,049.20