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	$220.65	7.189%	$236.5125	$236.51	$236.50	$236.50
Purchase #2	$237.81	11.740%	$265.7289	$265.73	$265.75	$265.70
Purchase #3	$60.83	10.165%	$67.0134	$67.01	$67.00	$67.00
Purchase #4	$218.63	13.270%	$247.6422	$247.64	$247.65	$247.60
Purchase #5	$45.66	6.123%	$48.4558	$48.46	$48.45	$48.50
Purchase #6	$73.93	6.255%	$78.5543	$78.55	$78.55	$78.60
Purchase #7	$185.93	9.466%	$203.5301	$203.53	$203.55	$203.50
7 purchase totals =	$1,043.44		$1,147.4372	$1,147.43	$1,147.45	$1,147.40