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	$174.33	12.605%	$196.3043	$196.30	$196.30	$196.30
Purchase #2	$197.69	12.665%	$222.7274	$222.73	$222.75	$222.70
Purchase #3	$141.84	8.648%	$154.1063	$154.11	$154.10	$154.10
Purchase #4	$158.58	12.217%	$177.9537	$177.95	$177.95	$178.00
Purchase #5	$102.59	13.497%	$116.4366	$116.44	$116.45	$116.40
Purchase #6	$128.78	6.216%	$136.785	$136.79	$136.80	$136.80
Purchase #7	$155.59	13.102%	$175.9754	$175.98	$176.00	$176.00
7 purchase totals =	$1,059.40		$1,180.2887	$1,180.30	$1,180.35	$1,180.30