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	$204.25	13.786%	$232.4079	$232.41	$232.40	$232.40
Purchase #2	$249.79	9.785%	$274.232	$274.23	$274.25	$274.20
Purchase #3	$201.45	10.571%	$222.7453	$222.75	$222.75	$222.70
Purchase #4	$154.32	3.594%	$159.8663	$159.87	$159.85	$159.90
Purchase #5	$27.71	5.112%	$29.1265	$29.13	$29.15	$29.10
Purchase #6	$34.47	9.181%	$37.6347	$37.63	$37.65	$37.60
Purchase #7	$86.58	3.705%	$89.7878	$89.79	$89.80	$89.80
7 purchase totals =	$958.57		$1,045.8005	$1,045.81	$1,045.85	$1,045.70