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	$34.33	10.750%	$38.0205	$38.02	$38.00	$38.00
Purchase #2	$52.49	12.484%	$59.0429	$59.04	$59.05	$59.00
Purchase #3	$209.55	9.302%	$229.0423	$229.04	$229.05	$229.00
Purchase #4	$60.89	7.628%	$65.5347	$65.53	$65.55	$65.50
Purchase #5	$65.43	9.192%	$71.4443	$71.44	$71.45	$71.40
Purchase #6	$87.86	8.394%	$95.235	$95.24	$95.25	$95.20
Purchase #7	$78.68	9.611%	$86.2419	$86.24	$86.25	$86.20
7 purchase totals =	$589.23		$644.5616	$644.55	$644.60	$644.30