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	$241.66	7.118%	$258.8614	$258.86	$258.85	$258.90
Purchase #2	$119.58	10.401%	$132.0175	$132.02	$132.00	$132.00
Purchase #3	$188.69	9.618%	$206.8382	$206.84	$206.85	$206.80
Purchase #4	$53.38	11.305%	$59.4146	$59.41	$59.40	$59.40
Purchase #5	$52.34	10.535%	$57.854	$57.85	$57.85	$57.90
Purchase #6	$101.70	11.555%	$113.4514	$113.45	$113.45	$113.50
Purchase #7	$177.55	12.681%	$200.0651	$200.07	$200.05	$200.10
7 purchase totals =	$934.90		$1,028.5022	$1,028.50	$1,028.45	$1,028.60