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	$138.54	8.846%	$150.7952	$150.80	$150.80	$150.80
Purchase #2	$172.95	13.784%	$196.7894	$196.79	$196.80	$196.80
Purchase #3	$72.96	11.681%	$81.4825	$81.48	$81.50	$81.50
Purchase #4	$177.31	12.497%	$199.4684	$199.47	$199.45	$199.50
Purchase #5	$61.57	6.433%	$65.5308	$65.53	$65.55	$65.50
Purchase #6	$233.54	3.664%	$242.0969	$242.10	$242.10	$242.10
Purchase #7	$118.88	8.315%	$128.7649	$128.76	$128.75	$128.80
7 purchase totals =	$975.75		$1,064.9281	$1,064.93	$1,064.95	$1,065.00