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	7.748%	$162.29	$162.29	$162.30	$162.30
Purchase #2	$149.39	12.615%	$168.2355	$168.24	$168.25	$168.20
Purchase #3	$155.59	9.127%	$169.7907	$169.79	$169.80	$169.80
Purchase #4	$140.71	5.310%	$148.1817	$148.18	$148.20	$148.20
Purchase #5	$100.90	12.226%	$113.236	$113.24	$113.25	$113.20
Purchase #6	$80.84	5.363%	$85.1754	$85.18	$85.20	$85.20
Purchase #7	$192.49	4.348%	$200.8595	$200.86	$200.85	$200.90
7 purchase totals =	$970.54		$1,047.7688	$1,047.78	$1,047.85	$1,047.80