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	$65.30	8.602%	$70.9171	$70.92	$70.90	$70.90
Purchase #2	$198.67	5.526%	$209.6485	$209.65	$209.65	$209.60
Purchase #3	$88.33	10.779%	$97.8511	$97.85	$97.85	$97.90
Purchase #4	$43.71	3.814%	$45.3771	$45.38	$45.40	$45.40
Purchase #5	$93.37	9.646%	$102.3765	$102.38	$102.40	$102.40
Purchase #6	$190.46	10.168%	$209.826	$209.83	$209.85	$209.80
Purchase #7	$194.54	3.249%	$200.8606	$200.86	$200.85	$200.90
7 purchase totals =	$874.38		$936.8569	$936.87	$936.90	$936.90