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	$206.26	4.800%	$216.1605	$216.16	$216.15	$216.20
Purchase #2	$236.89	11.433%	$263.9736	$263.97	$263.95	$264.00
Purchase #3	$187.91	4.778%	$196.8883	$196.89	$196.90	$196.90
Purchase #4	$81.58	13.343%	$92.4652	$92.47	$92.45	$92.50
Purchase #5	$113.69	7.503%	$122.2202	$122.22	$122.20	$122.20
Purchase #6	$168.59	5.857%	$178.4643	$178.46	$178.45	$178.50
Purchase #7	$243.95	12.738%	$275.0244	$275.02	$275.00	$275.00
7 purchase totals =	$1,238.87		$1,345.1965	$1,345.19	$1,345.10	$1,345.30