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	$109.41	9.546%	$119.8543	$119.85	$119.85	$119.90
Purchase #2	$154.51	11.432%	$172.1736	$172.17	$172.15	$172.20
Purchase #3	$93.99	4.477%	$98.1979	$98.20	$98.20	$98.20
Purchase #4	$186.40	12.324%	$209.3719	$209.37	$209.35	$209.40
Purchase #5	$113.58	8.707%	$123.4694	$123.47	$123.45	$123.50
Purchase #6	$132.81	9.528%	$145.4641	$145.46	$145.45	$145.50
Purchase #7	$100.97	11.164%	$112.2423	$112.24	$112.25	$112.20
7 purchase totals =	$891.67		$980.7735	$980.76	$980.70	$980.90