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	$75.52	10.548%	$83.4858	$83.49	$83.50	$83.50
Purchase #2	$199.41	11.330%	$222.0032	$222.00	$222.00	$222.00
Purchase #3	$97.39	3.537%	$100.8347	$100.83	$100.85	$100.80
Purchase #4	$24.79	6.813%	$26.4789	$26.48	$26.50	$26.50
Purchase #5	$185.67	10.336%	$204.8609	$204.86	$204.85	$204.90
Purchase #6	$238.51	12.741%	$268.8986	$268.90	$268.90	$268.90
Purchase #7	$133.45	4.768%	$139.8129	$139.81	$139.80	$139.80
7 purchase totals =	$954.74		$1,046.3750	$1,046.37	$1,046.40	$1,046.40