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	$149.93	12.233%	$168.2709	$168.27	$168.25	$168.30
Purchase #2	$70.83	8.255%	$76.677	$76.68	$76.70	$76.70
Purchase #3	$163.54	11.219%	$181.8876	$181.89	$181.90	$181.90
Purchase #4	$199.66	13.659%	$226.9316	$226.93	$226.95	$226.90
Purchase #5	$89.75	12.380%	$100.8611	$100.86	$100.85	$100.90
Purchase #6	$79.75	11.870%	$89.2163	$89.22	$89.20	$89.20
Purchase #7	$74.47	11.304%	$82.8881	$82.89	$82.90	$82.90
7 purchase totals =	$827.93		$926.7326	$926.74	$926.75	$926.80