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	$113.78	7.632%	$122.4637	$122.46	$122.45	$122.50
Purchase #2	$27.90	12.372%	$31.3518	$31.35	$31.35	$31.40
Purchase #3	$9.50	11.518%	$10.5942	$10.59	$10.60	$10.60
Purchase #4	$164.88	6.498%	$175.5939	$175.59	$175.60	$175.60
Purchase #5	$72.30	13.558%	$82.1024	$82.10	$82.10	$82.10
Purchase #6	$128.96	5.840%	$136.4913	$136.49	$136.50	$136.50
Purchase #7	$232.85	11.307%	$259.1783	$259.18	$259.20	$259.20
7 purchase totals =	$750.17		$817.7756	$817.76	$817.80	$817.90