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	$49.85	11.563%	$55.6142	$55.61	$55.60	$55.60
Purchase #2	$25.60	11.626%	$28.5763	$28.58	$28.60	$28.60
Purchase #3	$64.40	4.781%	$67.479	$67.48	$67.50	$67.50
Purchase #4	$56.34	9.148%	$61.494	$61.49	$61.50	$61.50
Purchase #5	$225.35	9.418%	$246.5735	$246.57	$246.55	$246.60
Purchase #6	$90.37	13.562%	$102.626	$102.63	$102.65	$102.60
Purchase #7	$16.54	12.376%	$18.587	$18.59	$18.60	$18.60
7 purchase totals =	$528.45		$580.9500	$580.95	$581.00	$581.00