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	$222.54	8.808%	$242.1413	$242.14	$242.15	$242.10
Purchase #2	$128.83	10.319%	$142.124	$142.12	$142.10	$142.10
Purchase #3	$16.94	8.388%	$18.3609	$18.36	$18.35	$18.40
Purchase #4	$9.90	5.826%	$10.4768	$10.48	$10.50	$10.50
Purchase #5	$153.84	9.591%	$168.5948	$168.59	$168.60	$168.60
Purchase #6	$212.30	7.611%	$228.4582	$228.46	$228.45	$228.50
Purchase #7	$189.34	11.641%	$211.3811	$211.38	$211.40	$211.40
7 purchase totals =	$933.69		$1,021.5371	$1,021.53	$1,021.55	$1,021.60