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	$74.94	10.315%	$82.6701	$82.67	$82.65	$82.70
Purchase #2	$194.26	6.173%	$206.2517	$206.25	$206.25	$206.30
Purchase #3	$30.38	11.556%	$33.8907	$33.89	$33.90	$33.90
Purchase #4	$37.98	6.519%	$40.4559	$40.46	$40.45	$40.50
Purchase #5	$233.67	11.358%	$260.2102	$260.21	$260.20	$260.20
Purchase #6	$41.79	12.391%	$46.9682	$46.97	$46.95	$47.00
Purchase #7	$100.34	11.482%	$111.861	$111.86	$111.85	$111.90
7 purchase totals =	$713.36		$782.3078	$782.31	$782.25	$782.50