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	$240.75	9.871%	$264.5144	$264.51	$264.50	$264.50
Purchase #2	$183.85	6.550%	$195.8922	$195.89	$195.90	$195.90
Purchase #3	$30.96	7.465%	$33.2712	$33.27	$33.25	$33.30
Purchase #4	$76.39	12.643%	$86.048	$86.05	$86.05	$86.00
Purchase #5	$123.33	6.587%	$131.4537	$131.45	$131.45	$131.50
Purchase #6	$196.59	11.116%	$218.4429	$218.44	$218.45	$218.40
Purchase #7	$169.58	13.702%	$192.8159	$192.82	$192.80	$192.80
7 purchase totals =	$1,021.45		$1,122.4383	$1,122.43	$1,122.40	$1,122.40