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	$29.95	9.871%	$32.9064	$32.91	$32.90	$32.90
Purchase #2	$17.89	5.471%	$18.8688	$18.87	$18.85	$18.90
Purchase #3	$47.65	12.133%	$53.4314	$53.43	$53.45	$53.40
Purchase #4	$159.85	3.565%	$165.5487	$165.55	$165.55	$165.50
Purchase #5	$89.67	3.824%	$93.099	$93.10	$93.10	$93.10
Purchase #6	$196.94	8.619%	$213.9143	$213.91	$213.90	$213.90
Purchase #7	$113.83	8.853%	$123.9074	$123.91	$123.90	$123.90
7 purchase totals =	$655.78		$701.6760	$701.68	$701.65	$701.60