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	$150.62	5.749%	$159.2791	$159.28	$159.30	$159.30
Purchase #2	$63.52	10.540%	$70.215	$70.22	$70.20	$70.20
Purchase #3	$126.85	13.854%	$144.4238	$144.42	$144.40	$144.40
Purchase #4	$67.41	5.321%	$70.9969	$71.00	$71.00	$71.00
Purchase #5	$136.83	12.385%	$153.7764	$153.78	$153.80	$153.80
Purchase #6	$94.97	3.742%	$98.5238	$98.52	$98.50	$98.50
Purchase #7	$242.77	12.496%	$273.1065	$273.11	$273.10	$273.10
7 purchase totals =	$882.97		$970.3215	$970.33	$970.30	$970.30