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	$206.43	9.481%	$226.0016	$226.00	$226.00	$226.00
Purchase #2	$129.49	6.195%	$137.5119	$137.51	$137.50	$137.50
Purchase #3	$54.33	9.275%	$59.3691	$59.37	$59.35	$59.40
Purchase #4	$79.95	11.236%	$88.9332	$88.93	$88.95	$88.90
Purchase #5	$80.70	9.681%	$88.5126	$88.51	$88.50	$88.50
Purchase #6	$37.26	3.556%	$38.585	$38.59	$38.60	$38.60
Purchase #7	$64.68	10.330%	$71.3614	$71.36	$71.35	$71.40
7 purchase totals =	$652.84		$710.2748	$710.27	$710.25	$710.30