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	$239.86	4.864%	$251.5268	$251.53	$251.55	$251.50
Purchase #2	$139.25	10.567%	$153.9645	$153.96	$153.95	$154.00
Purchase #3	$80.34	11.750%	$89.78	$89.78	$89.80	$89.80
Purchase #4	$102.71	7.324%	$110.2325	$110.23	$110.25	$110.20
Purchase #5	$170.66	5.820%	$180.5924	$180.59	$180.60	$180.60
Purchase #6	$74.56	9.359%	$81.5381	$81.54	$81.55	$81.50
Purchase #7	$130.78	13.849%	$148.8917	$148.89	$148.90	$148.90
7 purchase totals =	$938.16		$1,016.5260	$1,016.52	$1,016.60	$1,016.50