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	$80.66	11.260%	$89.7423	$89.74	$89.75	$89.70
Purchase #2	$110.50	7.500%	$118.7875	$118.79	$118.80	$118.80
Purchase #3	$232.54	4.735%	$243.5508	$243.55	$243.55	$243.60
Purchase #4	$182.79	12.661%	$205.933	$205.93	$205.95	$205.90
Purchase #5	$94.77	5.431%	$99.917	$99.92	$99.90	$99.90
Purchase #6	$59.43	11.122%	$66.0398	$66.04	$66.05	$66.00
Purchase #7	$116.58	8.866%	$126.916	$126.92	$126.90	$126.90
7 purchase totals =	$877.27		$950.8864	$950.89	$950.90	$950.80