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	$134.51	9.170%	$146.8446	$146.84	$146.85	$146.80
Purchase #2	$42.67	12.362%	$47.9449	$47.94	$47.95	$47.90
Purchase #3	$41.74	10.831%	$46.2609	$46.26	$46.25	$46.30
Purchase #4	$182.86	7.631%	$196.814	$196.81	$196.80	$196.80
Purchase #5	$31.89	6.611%	$33.9982	$34.00	$34.00	$34.00
Purchase #6	$50.71	4.305%	$52.8931	$52.89	$52.90	$52.90
Purchase #7	$167.93	6.775%	$179.3073	$179.31	$179.30	$179.30
7 purchase totals =	$652.31		$704.0630	$704.05	$704.05	$704.00