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	$50.82	8.726%	$55.2546	$55.25	$55.25	$55.30
Purchase #2	$91.49	11.368%	$101.8906	$101.89	$101.90	$101.90
Purchase #3	$173.95	11.752%	$194.3926	$194.39	$194.40	$194.40
Purchase #4	$196.69	12.578%	$221.4297	$221.43	$221.45	$221.40
Purchase #5	$237.85	8.679%	$258.493	$258.49	$258.50	$258.50
Purchase #6	$64.32	12.471%	$72.3413	$72.34	$72.35	$72.30
Purchase #7	$156.72	3.341%	$161.956	$161.96	$161.95	$162.00
7 purchase totals =	$971.84		$1,065.7578	$1,065.75	$1,065.80	$1,065.80