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	$44.46	3.226%	$45.8943	$45.89	$45.90	$45.90
Purchase #2	$131.73	3.833%	$136.7792	$136.78	$136.80	$136.80
Purchase #3	$163.96	10.781%	$181.6365	$181.64	$181.65	$181.60
Purchase #4	$91.72	11.665%	$102.4191	$102.42	$102.40	$102.40
Purchase #5	$61.64	5.270%	$64.8884	$64.89	$64.90	$64.90
Purchase #6	$235.61	8.788%	$256.3154	$256.32	$256.30	$256.30
Purchase #7	$224.59	8.437%	$243.5387	$243.54	$243.55	$243.50
7 purchase totals =	$953.71		$1,031.4716	$1,031.48	$1,031.50	$1,031.40