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	$112.66	12.628%	$126.8867	$126.89	$126.90	$126.90
Purchase #2	$93.56	11.147%	$103.9891	$103.99	$104.00	$104.00
Purchase #3	$11.98	7.725%	$12.9055	$12.91	$12.90	$12.90
Purchase #4	$132.52	11.576%	$147.8605	$147.86	$147.85	$147.90
Purchase #5	$89.40	11.362%	$99.5576	$99.56	$99.55	$99.60
Purchase #6	$151.46	3.815%	$157.2382	$157.24	$157.25	$157.20
Purchase #7	$125.29	8.800%	$136.3155	$136.32	$136.30	$136.30
7 purchase totals =	$716.87		$784.7531	$784.77	$784.75	$784.80