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	$223.52	8.542%	$242.6131	$242.61	$242.60	$242.60
Purchase #2	$59.67	13.661%	$67.8215	$67.82	$67.80	$67.80
Purchase #3	$217.86	11.374%	$242.6394	$242.64	$242.65	$242.60
Purchase #4	$221.77	13.464%	$251.6291	$251.63	$251.65	$251.60
Purchase #5	$53.76	12.526%	$60.494	$60.49	$60.50	$60.50
Purchase #6	$95.46	8.412%	$103.4901	$103.49	$103.50	$103.50
Purchase #7	$82.79	7.542%	$89.034	$89.03	$89.05	$89.00
7 purchase totals =	$954.83		$1,057.7212	$1,057.71	$1,057.75	$1,057.60