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	$9.99	11.496%	$11.1385	$11.14	$11.15	$11.10
Purchase #2	$56.60	4.250%	$59.0055	$59.01	$59.00	$59.00
Purchase #3	$163.81	7.823%	$176.6249	$176.62	$176.60	$176.60
Purchase #4	$200.78	7.142%	$215.1197	$215.12	$215.10	$215.10
Purchase #5	$67.62	6.328%	$71.899	$71.90	$71.90	$71.90
Purchase #6	$113.90	9.570%	$124.8002	$124.80	$124.80	$124.80
Purchase #7	$40.78	6.475%	$43.4205	$43.42	$43.40	$43.40
7 purchase totals =	$653.48		$702.0083	$702.01	$701.95	$701.90