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	$126.50	3.585%	$131.035	$131.04	$131.05	$131.00
Purchase #2	$36.84	5.495%	$38.8644	$38.86	$38.85	$38.90
Purchase #3	$29.34	8.455%	$31.8207	$31.82	$31.80	$31.80
Purchase #4	$87.38	8.634%	$94.9244	$94.92	$94.90	$94.90
Purchase #5	$100.45	12.819%	$113.3267	$113.33	$113.35	$113.30
Purchase #6	$96.53	10.809%	$106.9639	$106.96	$106.95	$107.00
Purchase #7	$159.49	5.536%	$168.3194	$168.32	$168.30	$168.30
7 purchase totals =	$636.53		$685.2545	$685.25	$685.20	$685.20