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	$179.56	11.304%	$199.8575	$199.86	$199.85	$199.90
Purchase #2	$88.67	13.300%	$100.4631	$100.46	$100.45	$100.50
Purchase #3	$65.42	3.373%	$67.6266	$67.63	$67.65	$67.60
Purchase #4	$53.91	3.416%	$55.7516	$55.75	$55.75	$55.80
Purchase #5	$33.68	12.168%	$37.7782	$37.78	$37.80	$37.80
Purchase #6	$29.41	9.694%	$32.261	$32.26	$32.25	$32.30
Purchase #7	$80.71	4.338%	$84.2112	$84.21	$84.20	$84.20
7 purchase totals =	$531.36		$577.9492	$577.95	$577.95	$578.10