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	$218.27	6.125%	$231.639	$231.64	$231.65	$231.60
Purchase #2	$189.91	11.181%	$211.1438	$211.14	$211.15	$211.10
Purchase #3	$214.97	8.321%	$232.8577	$232.86	$232.85	$232.90
Purchase #4	$78.59	13.771%	$89.4126	$89.41	$89.40	$89.40
Purchase #5	$34.72	6.426%	$36.9511	$36.95	$36.95	$37.00
Purchase #6	$81.42	5.529%	$85.9217	$85.92	$85.90	$85.90
Purchase #7	$133.48	12.872%	$150.6615	$150.66	$150.65	$150.70
7 purchase totals =	$951.36		$1,038.5874	$1,038.58	$1,038.55	$1,038.60