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	$250.25	4.142%	$260.6154	$260.62	$260.60	$260.60
Purchase #2	$36.95	7.488%	$39.7168	$39.72	$39.70	$39.70
Purchase #3	$117.48	9.425%	$128.5525	$128.55	$128.55	$128.60
Purchase #4	$92.57	10.144%	$101.9603	$101.96	$101.95	$102.00
Purchase #5	$155.90	8.564%	$169.2513	$169.25	$169.25	$169.30
Purchase #6	$182.68	7.452%	$196.2933	$196.29	$196.30	$196.30
Purchase #7	$32.42	9.621%	$35.5391	$35.54	$35.55	$35.50
7 purchase totals =	$868.25		$931.9287	$931.93	$931.90	$932.00