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	$92.54	13.161%	$104.7192	$104.72	$104.70	$104.70
Purchase #2	$95.43	4.207%	$99.4447	$99.44	$99.45	$99.40
Purchase #3	$89.82	13.490%	$101.9367	$101.94	$101.95	$101.90
Purchase #4	$150.84	5.181%	$158.655	$158.66	$158.65	$158.70
Purchase #5	$206.31	8.481%	$223.8072	$223.81	$223.80	$223.80
Purchase #6	$60.78	8.452%	$65.9171	$65.92	$65.90	$65.90
Purchase #7	$123.90	12.563%	$139.4656	$139.47	$139.45	$139.50
7 purchase totals =	$819.62		$893.9455	$893.96	$893.90	$893.90