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	$118.67	6.598%	$126.4998	$126.50	$126.50	$126.50
Purchase #2	$37.67	11.467%	$41.9896	$41.99	$42.00	$42.00
Purchase #3	$161.46	13.662%	$183.5187	$183.52	$183.50	$183.50
Purchase #4	$215.89	13.681%	$245.4259	$245.43	$245.45	$245.40
Purchase #5	$98.77	13.781%	$112.3815	$112.38	$112.40	$112.40
Purchase #6	$81.31	9.226%	$88.8117	$88.81	$88.80	$88.80
Purchase #7	$111.98	13.426%	$127.0144	$127.01	$127.00	$127.00
7 purchase totals =	$825.75		$925.6416	$925.64	$925.65	$925.60