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	$73.46	13.747%	$83.5585	$83.56	$83.55	$83.60
Purchase #2	$145.39	6.617%	$155.0105	$155.01	$155.00	$155.00
Purchase #3	$166.92	11.120%	$185.4815	$185.48	$185.50	$185.50
Purchase #4	$144.69	13.690%	$164.4981	$164.50	$164.50	$164.50
Purchase #5	$88.67	4.795%	$92.9217	$92.92	$92.90	$92.90
Purchase #6	$40.94	12.217%	$45.9416	$45.94	$45.95	$45.90
Purchase #7	$174.71	8.372%	$189.3367	$189.34	$189.35	$189.30
7 purchase totals =	$834.78		$916.7486	$916.75	$916.75	$916.70