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	$212.84	12.200%	$238.8065	$238.81	$238.80	$238.80
Purchase #2	$184.83	4.418%	$192.9958	$193.00	$193.00	$193.00
Purchase #3	$39.30	6.644%	$41.9111	$41.91	$41.90	$41.90
Purchase #4	$184.48	6.291%	$196.0856	$196.09	$196.10	$196.10
Purchase #5	$248.26	12.579%	$279.4886	$279.49	$279.50	$279.50
Purchase #6	$149.25	13.807%	$169.8569	$169.86	$169.85	$169.90
Purchase #7	$100.40	4.303%	$104.7202	$104.72	$104.70	$104.70
7 purchase totals =	$1,119.36		$1,223.8647	$1,223.88	$1,223.85	$1,223.90