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	$198.41	13.364%	$224.9255	$224.93	$224.95	$224.90
Purchase #2	$235.50	8.376%	$255.2255	$255.23	$255.25	$255.20
Purchase #3	$209.25	7.632%	$225.22	$225.22	$225.20	$225.20
Purchase #4	$60.48	10.702%	$66.9526	$66.95	$66.95	$67.00
Purchase #5	$25.38	7.384%	$27.2541	$27.25	$27.25	$27.30
Purchase #6	$114.84	4.838%	$120.396	$120.40	$120.40	$120.40
Purchase #7	$94.89	5.805%	$100.3984	$100.40	$100.40	$100.40
7 purchase totals =	$938.75		$1,020.3721	$1,020.38	$1,020.40	$1,020.40