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	$32.25	8.153%	$34.8793	$34.88	$34.90	$34.90
Purchase #2	$86.64	8.374%	$93.8952	$93.90	$93.90	$93.90
Purchase #3	$144.41	11.835%	$161.5009	$161.50	$161.50	$161.50
Purchase #4	$49.63	3.298%	$51.2668	$51.27	$51.25	$51.30
Purchase #5	$112.69	3.574%	$116.7175	$116.72	$116.70	$116.70
Purchase #6	$50.46	6.790%	$53.8862	$53.89	$53.90	$53.90
Purchase #7	$50.79	7.871%	$54.7877	$54.79	$54.80	$54.80
7 purchase totals =	$526.87		$566.9336	$566.95	$566.95	$567.00