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	$65.56	9.486%	$71.779	$71.78	$71.80	$71.80
Purchase #2	$66.82	9.695%	$73.2982	$73.30	$73.30	$73.30
Purchase #3	$86.59	6.535%	$92.2487	$92.25	$92.25	$92.20
Purchase #4	$139.66	4.740%	$146.2799	$146.28	$146.30	$146.30
Purchase #5	$128.46	8.537%	$139.4266	$139.43	$139.45	$139.40
Purchase #6	$89.25	9.684%	$97.893	$97.89	$97.90	$97.90
Purchase #7	$103.92	12.507%	$116.9173	$116.92	$116.90	$116.90
7 purchase totals =	$680.26		$737.8427	$737.85	$737.90	$737.80