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	$82.79	4.787%	$86.7532	$86.75	$86.75	$86.80
Purchase #2	$236.83	11.837%	$264.8636	$264.86	$264.85	$264.90
Purchase #3	$34.90	5.567%	$36.8429	$36.84	$36.85	$36.80
Purchase #4	$85.93	3.580%	$89.0063	$89.01	$89.00	$89.00
Purchase #5	$134.36	6.357%	$142.9013	$142.90	$142.90	$142.90
Purchase #6	$88.88	9.190%	$97.0481	$97.05	$97.05	$97.00
Purchase #7	$35.46	4.405%	$37.022	$37.02	$37.00	$37.00
7 purchase totals =	$699.15		$754.4374	$754.43	$754.40	$754.40