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	$156.37	7.207%	$167.6396	$167.64	$167.65	$167.60
Purchase #2	$122.88	6.666%	$131.0712	$131.07	$131.05	$131.10
Purchase #3	$179.49	11.712%	$200.5119	$200.51	$200.50	$200.50
Purchase #4	$241.28	3.331%	$249.317	$249.32	$249.30	$249.30
Purchase #5	$7.92	12.653%	$8.9221	$8.92	$8.90	$8.90
Purchase #6	$20.33	10.577%	$22.4803	$22.48	$22.50	$22.50
Purchase #7	$234.78	10.863%	$260.2842	$260.28	$260.30	$260.30
7 purchase totals =	$963.05		$1,040.2263	$1,040.22	$1,040.20	$1,040.20