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	$76.78	12.452%	$86.3406	$86.34	$86.35	$86.30
Purchase #2	$142.70	7.131%	$152.8759	$152.88	$152.90	$152.90
Purchase #3	$41.55	5.395%	$43.7916	$43.79	$43.80	$43.80
Purchase #4	$243.46	12.727%	$274.4452	$274.45	$274.45	$274.40
Purchase #5	$200.53	4.663%	$209.8807	$209.88	$209.90	$209.90
Purchase #6	$36.98	10.272%	$40.7786	$40.78	$40.80	$40.80
Purchase #7	$148.46	4.575%	$155.252	$155.25	$155.25	$155.30
7 purchase totals =	$890.46		$963.3646	$963.37	$963.45	$963.40