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	$107.31	3.848%	$111.4393	$111.44	$111.45	$111.40
Purchase #2	$64.31	8.238%	$69.6079	$69.61	$69.60	$69.60
Purchase #3	$122.80	6.849%	$131.2106	$131.21	$131.20	$131.20
Purchase #4	$50.36	9.345%	$55.0661	$55.07	$55.05	$55.10
Purchase #5	$40.27	4.307%	$42.0044	$42.00	$42.00	$42.00
Purchase #6	$67.74	13.620%	$76.9662	$76.97	$76.95	$77.00
Purchase #7	$142.28	13.757%	$161.8535	$161.85	$161.85	$161.90
7 purchase totals =	$595.07		$648.1480	$648.15	$648.10	$648.20