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	$95.55	10.701%	$105.7748	$105.77	$105.75	$105.80
Purchase #2	$246.93	10.296%	$272.3539	$272.35	$272.35	$272.40
Purchase #3	$84.95	6.867%	$90.7835	$90.78	$90.80	$90.80
Purchase #4	$224.91	13.615%	$255.5315	$255.53	$255.55	$255.50
Purchase #5	$143.88	12.282%	$161.5513	$161.55	$161.55	$161.60
Purchase #6	$125.26	5.312%	$131.9138	$131.91	$131.90	$131.90
Purchase #7	$31.93	4.321%	$33.3097	$33.31	$33.30	$33.30
7 purchase totals =	$953.41		$1,051.2185	$1,051.20	$1,051.20	$1,051.30