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	$96.66	6.530%	$102.9719	$102.97	$102.95	$103.00
Purchase #2	$143.79	8.560%	$156.0984	$156.10	$156.10	$156.10
Purchase #3	$112.47	6.291%	$119.5455	$119.55	$119.55	$119.50
Purchase #4	$206.49	7.596%	$222.175	$222.18	$222.20	$222.20
Purchase #5	$155.25	8.369%	$168.2429	$168.24	$168.25	$168.20
Purchase #6	$119.50	11.617%	$133.3823	$133.38	$133.40	$133.40
Purchase #7	$205.27	11.787%	$229.4652	$229.47	$229.45	$229.50
7 purchase totals =	$1,039.43		$1,131.8812	$1,131.89	$1,131.90	$1,131.90