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	$67.28	7.841%	$72.5554	$72.56	$72.55	$72.60
Purchase #2	$175.58	7.783%	$189.2454	$189.25	$189.25	$189.20
Purchase #3	$154.94	10.587%	$171.3435	$171.34	$171.35	$171.30
Purchase #4	$6.25	13.871%	$7.1169	$7.12	$7.10	$7.10
Purchase #5	$213.57	4.573%	$223.3366	$223.34	$223.35	$223.30
Purchase #6	$244.35	4.595%	$255.5779	$255.58	$255.60	$255.60
Purchase #7	$115.56	8.321%	$125.1757	$125.18	$125.20	$125.20
7 purchase totals =	$977.53		$1,044.3514	$1,044.37	$1,044.40	$1,044.30