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	$105.83	9.860%	$116.2648	$116.26	$116.25	$116.30
Purchase #2	$170.83	13.850%	$194.49	$194.49	$194.50	$194.50
Purchase #3	$185.57	12.182%	$208.1761	$208.18	$208.20	$208.20
Purchase #4	$125.57	12.299%	$141.0139	$141.01	$141.00	$141.00
Purchase #5	$91.97	12.266%	$103.251	$103.25	$103.25	$103.30
Purchase #6	$121.34	7.806%	$130.8118	$130.81	$130.80	$130.80
Purchase #7	$226.30	3.230%	$233.6095	$233.61	$233.60	$233.60
7 purchase totals =	$1,027.41		$1,127.6171	$1,127.61	$1,127.60	$1,127.70