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	$54.95	4.601%	$57.4782	$57.48	$57.50	$57.50
Purchase #2	$196.86	4.335%	$205.3939	$205.39	$205.40	$205.40
Purchase #3	$121.59	10.441%	$134.2852	$134.29	$134.30	$134.30
Purchase #4	$27.76	10.796%	$30.757	$30.76	$30.75	$30.80
Purchase #5	$164.52	11.164%	$182.887	$182.89	$182.90	$182.90
Purchase #6	$63.91	12.562%	$71.9384	$71.94	$71.95	$71.90
Purchase #7	$27.31	9.515%	$29.9085	$29.91	$29.90	$29.90
7 purchase totals =	$656.90		$712.6482	$712.66	$712.70	$712.70