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	$192.72	5.380%	$203.0883	$203.09	$203.10	$203.10
Purchase #2	$56.59	9.581%	$62.0119	$62.01	$62.00	$62.00
Purchase #3	$104.66	6.569%	$111.5351	$111.54	$111.55	$111.50
Purchase #4	$36.95	5.145%	$38.8511	$38.85	$38.85	$38.90
Purchase #5	$198.79	13.465%	$225.5571	$225.56	$225.55	$225.60
Purchase #6	$102.58	6.427%	$109.1728	$109.17	$109.15	$109.20
Purchase #7	$112.48	7.401%	$120.8046	$120.80	$120.80	$120.80
7 purchase totals =	$804.77		$871.0209	$871.02	$871.00	$871.10