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	$195.32	13.462%	$221.614	$221.61	$221.60	$221.60
Purchase #2	$7.62	8.625%	$8.2772	$8.28	$8.30	$8.30
Purchase #3	$90.79	11.126%	$100.8913	$100.89	$100.90	$100.90
Purchase #4	$19.31	7.416%	$20.742	$20.74	$20.75	$20.70
Purchase #5	$91.88	3.683%	$95.2639	$95.26	$95.25	$95.30
Purchase #6	$236.89	13.207%	$268.1761	$268.18	$268.20	$268.20
Purchase #7	$74.99	10.456%	$82.831	$82.83	$82.85	$82.80
7 purchase totals =	$716.80		$797.7955	$797.79	$797.85	$797.80