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	$196.88	12.835%	$222.1495	$222.15	$222.15	$222.10
Purchase #2	$169.30	11.689%	$189.0895	$189.09	$189.10	$189.10
Purchase #3	$185.28	10.347%	$204.4509	$204.45	$204.45	$204.50
Purchase #4	$30.28	7.265%	$32.4798	$32.48	$32.50	$32.50
Purchase #5	$28.52	10.638%	$31.554	$31.55	$31.55	$31.60
Purchase #6	$160.28	13.853%	$182.4836	$182.48	$182.50	$182.50
Purchase #7	$51.25	3.154%	$52.8664	$52.87	$52.85	$52.90
7 purchase totals =	$821.79		$915.0737	$915.07	$915.10	$915.20