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	$209.61	11.364%	$233.4301	$233.43	$233.45	$233.40
Purchase #2	$128.29	10.278%	$141.4756	$141.48	$141.50	$141.50
Purchase #3	$103.33	7.434%	$111.0116	$111.01	$111.00	$111.00
Purchase #4	$124.36	12.822%	$140.3054	$140.31	$140.30	$140.30
Purchase #5	$133.66	6.398%	$142.2116	$142.21	$142.20	$142.20
Purchase #6	$189.29	10.367%	$208.9137	$208.91	$208.90	$208.90
Purchase #7	$95.38	5.167%	$100.3083	$100.31	$100.30	$100.30
7 purchase totals =	$983.92		$1,077.6563	$1,077.66	$1,077.65	$1,077.60