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	$194.78	9.296%	$212.8867	$212.89	$212.90	$212.90
Purchase #2	$173.43	9.660%	$190.1833	$190.18	$190.20	$190.20
Purchase #3	$170.33	7.631%	$183.3279	$183.33	$183.35	$183.30
Purchase #4	$232.67	4.158%	$242.3444	$242.34	$242.35	$242.30
Purchase #5	$161.44	4.394%	$168.5337	$168.53	$168.55	$168.50
Purchase #6	$187.66	4.849%	$196.7596	$196.76	$196.75	$196.80
Purchase #7	$114.41	10.145%	$126.0169	$126.02	$126.00	$126.00
7 purchase totals =	$1,234.72		$1,320.0525	$1,320.05	$1,320.10	$1,320.00