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	$107.48	10.712%	$118.9933	$118.99	$119.00	$119.00
Purchase #2	$225.62	11.368%	$251.2685	$251.27	$251.25	$251.30
Purchase #3	$33.70	8.223%	$36.4712	$36.47	$36.45	$36.50
Purchase #4	$236.58	8.583%	$256.8857	$256.89	$256.90	$256.90
Purchase #5	$70.50	10.871%	$78.1641	$78.16	$78.15	$78.20
Purchase #6	$190.80	4.782%	$199.9241	$199.92	$199.90	$199.90
Purchase #7	$86.57	12.578%	$97.4588	$97.46	$97.45	$97.50
7 purchase totals =	$951.25		$1,039.1657	$1,039.16	$1,039.10	$1,039.30