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	$142.34	9.437%	$155.7726	$155.77	$155.75	$155.80
Purchase #2	$218.46	11.297%	$243.1394	$243.14	$243.15	$243.10
Purchase #3	$99.96	8.443%	$108.3996	$108.40	$108.40	$108.40
Purchase #4	$188.36	10.674%	$208.4655	$208.47	$208.45	$208.50
Purchase #5	$53.34	10.650%	$59.0207	$59.02	$59.00	$59.00
Purchase #6	$188.81	5.409%	$199.0227	$199.02	$199.00	$199.00
Purchase #7	$125.50	11.367%	$139.7656	$139.77	$139.75	$139.80
7 purchase totals =	$1,016.77		$1,113.5861	$1,113.59	$1,113.50	$1,113.60