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	$196.86	11.480%	$219.4595	$219.46	$219.45	$219.50
Purchase #2	$248.52	9.323%	$271.6895	$271.69	$271.70	$271.70
Purchase #3	$143.98	3.124%	$148.4779	$148.48	$148.50	$148.50
Purchase #4	$120.49	6.778%	$128.6568	$128.66	$128.65	$128.70
Purchase #5	$162.66	5.272%	$171.2354	$171.24	$171.25	$171.20
Purchase #6	$202.90	9.375%	$221.9219	$221.92	$221.90	$221.90
Purchase #7	$54.72	13.358%	$62.0295	$62.03	$62.05	$62.00
7 purchase totals =	$1,130.13		$1,223.4705	$1,223.48	$1,223.50	$1,223.50