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	$203.96	7.298%	$218.845	$218.85	$218.85	$218.80
Purchase #2	$41.69	12.490%	$46.8971	$46.90	$46.90	$46.90
Purchase #3	$179.40	3.525%	$185.7239	$185.72	$185.70	$185.70
Purchase #4	$247.73	7.349%	$265.9357	$265.94	$265.95	$265.90
Purchase #5	$37.95	10.611%	$41.9769	$41.98	$42.00	$42.00
Purchase #6	$164.89	6.855%	$176.1932	$176.19	$176.20	$176.20
Purchase #7	$128.38	10.390%	$141.7187	$141.72	$141.70	$141.70
7 purchase totals =	$1,004.00		$1,077.2905	$1,077.30	$1,077.30	$1,077.20