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	$40.25	13.427%	$45.6544	$45.65	$45.65	$45.70
Purchase #2	$133.66	4.214%	$139.2924	$139.29	$139.30	$139.30
Purchase #3	$156.60	12.166%	$175.652	$175.65	$175.65	$175.70
Purchase #4	$244.73	4.554%	$255.875	$255.88	$255.90	$255.90
Purchase #5	$57.62	13.829%	$65.5883	$65.59	$65.60	$65.60
Purchase #6	$216.86	5.671%	$229.1581	$229.16	$229.15	$229.20
Purchase #7	$168.57	9.264%	$184.1863	$184.19	$184.20	$184.20
7 purchase totals =	$1,018.29		$1,095.4065	$1,095.41	$1,095.45	$1,095.60