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	$30.97	3.500%	$32.054	$32.05	$32.05	$32.10
Purchase #2	$191.47	9.108%	$208.9091	$208.91	$208.90	$208.90
Purchase #3	$177.25	8.787%	$192.825	$192.83	$192.85	$192.80
Purchase #4	$87.83	4.483%	$91.7674	$91.77	$91.75	$91.80
Purchase #5	$233.64	4.392%	$243.9015	$243.90	$243.90	$243.90
Purchase #6	$192.77	3.632%	$199.7714	$199.77	$199.75	$199.80
Purchase #7	$40.80	6.285%	$43.3643	$43.36	$43.35	$43.40
7 purchase totals =	$954.73		$1,012.5927	$1,012.59	$1,012.55	$1,012.70