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	$44.60	4.834%	$46.756	$46.76	$46.75	$46.80
Purchase #2	$59.81	4.394%	$62.4381	$62.44	$62.45	$62.40
Purchase #3	$131.83	5.818%	$139.4999	$139.50	$139.50	$139.50
Purchase #4	$44.57	6.687%	$47.5504	$47.55	$47.55	$47.60
Purchase #5	$100.87	5.606%	$106.5248	$106.52	$106.50	$106.50
Purchase #6	$183.96	13.161%	$208.171	$208.17	$208.15	$208.20
Purchase #7	$77.53	11.681%	$86.5863	$86.59	$86.60	$86.60
7 purchase totals =	$643.17		$697.5265	$697.53	$697.50	$697.60