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	$13.50	4.342%	$14.0862	$14.09	$14.10	$14.10
Purchase #2	$80.50	12.402%	$90.4836	$90.48	$90.50	$90.50
Purchase #3	$35.67	13.805%	$40.5942	$40.59	$40.60	$40.60
Purchase #4	$244.65	3.417%	$253.0097	$253.01	$253.00	$253.00
Purchase #5	$113.65	4.373%	$118.6199	$118.62	$118.60	$118.60
Purchase #6	$227.38	12.149%	$255.0044	$255.00	$255.00	$255.00
Purchase #7	$190.73	12.782%	$215.1091	$215.11	$215.10	$215.10
7 purchase totals =	$906.08		$986.9071	$986.90	$986.90	$986.90