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	$37.43	7.831%	$40.3611	$40.36	$40.35	$40.40
Purchase #2	$109.57	4.443%	$114.4382	$114.44	$114.45	$114.40
Purchase #3	$249.59	4.672%	$261.2508	$261.25	$261.25	$261.30
Purchase #4	$81.36	3.663%	$84.3402	$84.34	$84.35	$84.30
Purchase #5	$100.91	10.562%	$111.5681	$111.57	$111.55	$111.60
Purchase #6	$220.66	3.123%	$227.5512	$227.55	$227.55	$227.60
Purchase #7	$96.31	9.392%	$105.3554	$105.36	$105.35	$105.40
7 purchase totals =	$895.83		$944.8650	$944.87	$944.85	$945.00