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	$100.86	7.351%	$108.2742	$108.27	$108.25	$108.30
Purchase #2	$222.87	4.611%	$233.1465	$233.15	$233.15	$233.10
Purchase #3	$29.26	12.359%	$32.8762	$32.88	$32.90	$32.90
Purchase #4	$188.89	10.490%	$208.7046	$208.70	$208.70	$208.70
Purchase #5	$139.56	10.591%	$154.3408	$154.34	$154.35	$154.30
Purchase #6	$179.59	7.142%	$192.4163	$192.42	$192.40	$192.40
Purchase #7	$77.50	7.729%	$83.49	$83.49	$83.50	$83.50
7 purchase totals =	$938.53		$1,013.2486	$1,013.25	$1,013.25	$1,013.20