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	$29.92	10.116%	$32.9467	$32.95	$32.95	$32.90
Purchase #2	$175.68	3.804%	$182.3629	$182.36	$182.35	$182.40
Purchase #3	$116.84	9.860%	$128.3604	$128.36	$128.35	$128.40
Purchase #4	$200.28	12.456%	$225.2269	$225.23	$225.25	$225.20
Purchase #5	$84.70	7.321%	$90.9009	$90.90	$90.90	$90.90
Purchase #6	$85.92	11.426%	$95.7372	$95.74	$95.75	$95.70
Purchase #7	$131.69	6.266%	$139.9417	$139.94	$139.95	$139.90
7 purchase totals =	$825.03		$895.4767	$895.48	$895.50	$895.40