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	$87.88	6.799%	$93.855	$93.86	$93.85	$93.90
Purchase #2	$143.57	3.151%	$148.0939	$148.09	$148.10	$148.10
Purchase #3	$145.34	4.558%	$151.9646	$151.96	$151.95	$152.00
Purchase #4	$123.66	10.372%	$136.486	$136.49	$136.50	$136.50
Purchase #5	$186.67	11.871%	$208.8296	$208.83	$208.85	$208.80
Purchase #6	$170.41	7.686%	$183.5077	$183.51	$183.50	$183.50
Purchase #7	$101.89	6.109%	$108.1145	$108.11	$108.10	$108.10
7 purchase totals =	$959.42		$1,030.8513	$1,030.85	$1,030.85	$1,030.90