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	$218.28	12.587%	$245.7549	$245.75	$245.75	$245.80
Purchase #2	$186.29	7.496%	$200.2543	$200.25	$200.25	$200.30
Purchase #3	$119.67	7.626%	$128.796	$128.80	$128.80	$128.80
Purchase #4	$187.45	4.637%	$196.1421	$196.14	$196.15	$196.10
Purchase #5	$231.85	10.148%	$255.3781	$255.38	$255.40	$255.40
Purchase #6	$9.37	7.572%	$10.0795	$10.08	$10.10	$10.10
Purchase #7	$78.57	4.118%	$81.8055	$81.81	$81.80	$81.80
7 purchase totals =	$1,031.48		$1,118.2104	$1,118.21	$1,118.25	$1,118.30