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	$13.75	7.295%	$14.7531	$14.75	$14.75	$14.80
Purchase #2	$65.81	9.588%	$72.1199	$72.12	$72.10	$72.10
Purchase #3	$193.78	9.384%	$211.9643	$211.96	$211.95	$212.00
Purchase #4	$19.96	6.375%	$21.2325	$21.23	$21.25	$21.20
Purchase #5	$30.76	5.230%	$32.3687	$32.37	$32.35	$32.40
Purchase #6	$16.80	8.458%	$18.2209	$18.22	$18.20	$18.20
Purchase #7	$93.81	6.856%	$100.2416	$100.24	$100.25	$100.20
7 purchase totals =	$434.67		$470.9010	$470.89	$470.85	$470.90