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	$121.27	13.742%	$137.9349	$137.93	$137.95	$137.90
Purchase #2	$77.61	7.805%	$83.6675	$83.67	$83.65	$83.70
Purchase #3	$184.89	7.697%	$199.121	$199.12	$199.10	$199.10
Purchase #4	$203.33	9.283%	$222.2051	$222.21	$222.20	$222.20
Purchase #5	$78.38	9.468%	$85.801	$85.80	$85.80	$85.80
Purchase #6	$169.64	11.721%	$189.5235	$189.52	$189.50	$189.50
Purchase #7	$138.41	13.850%	$157.5798	$157.58	$157.60	$157.60
7 purchase totals =	$973.53		$1,075.8328	$1,075.83	$1,075.80	$1,075.80