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	$110.51	6.445%	$117.6324	$117.63	$117.65	$117.60
Purchase #2	$71.44	13.703%	$81.2294	$81.23	$81.25	$81.20
Purchase #3	$33.53	11.752%	$37.4704	$37.47	$37.45	$37.50
Purchase #4	$72.90	10.408%	$80.4874	$80.49	$80.50	$80.50
Purchase #5	$166.28	13.671%	$189.0121	$189.01	$189.00	$189.00
Purchase #6	$221.31	4.530%	$231.3353	$231.34	$231.35	$231.30
Purchase #7	$118.58	10.294%	$130.7866	$130.79	$130.80	$130.80
7 purchase totals =	$794.55		$867.9536	$867.96	$868.00	$867.90