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	$222.96	10.397%	$246.1412	$246.14	$246.15	$246.10
Purchase #2	$235.75	3.256%	$243.426	$243.43	$243.45	$243.40
Purchase #3	$49.84	8.547%	$54.0998	$54.10	$54.10	$54.10
Purchase #4	$98.43	5.743%	$104.0828	$104.08	$104.10	$104.10
Purchase #5	$139.37	3.672%	$144.4877	$144.49	$144.50	$144.50
Purchase #6	$145.57	3.303%	$150.3782	$150.38	$150.40	$150.40
Purchase #7	$101.42	9.331%	$110.8835	$110.88	$110.90	$110.90
7 purchase totals =	$993.34		$1,053.4992	$1,053.50	$1,053.60	$1,053.50