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	$170.50	9.783%	$187.18	$187.18	$187.20	$187.20
Purchase #2	$213.95	8.376%	$231.8705	$231.87	$231.85	$231.90
Purchase #3	$171.73	11.186%	$190.9397	$190.94	$190.95	$190.90
Purchase #4	$165.56	6.549%	$176.4025	$176.40	$176.40	$176.40
Purchase #5	$140.41	12.642%	$158.1606	$158.16	$158.15	$158.20
Purchase #6	$86.73	9.708%	$95.1497	$95.15	$95.15	$95.10
Purchase #7	$43.94	3.649%	$45.5434	$45.54	$45.55	$45.50
7 purchase totals =	$992.82		$1,085.2464	$1,085.24	$1,085.25	$1,085.20