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	$82.77	10.627%	$91.566	$91.57	$91.55	$91.60
Purchase #2	$199.44	13.545%	$226.4541	$226.45	$226.45	$226.50
Purchase #3	$12.39	6.743%	$13.2255	$13.23	$13.25	$13.20
Purchase #4	$38.33	10.539%	$42.3696	$42.37	$42.35	$42.40
Purchase #5	$31.61	10.382%	$34.8918	$34.89	$34.90	$34.90
Purchase #6	$103.67	8.680%	$112.6686	$112.67	$112.65	$112.70
Purchase #7	$171.76	4.378%	$179.2797	$179.28	$179.30	$179.30
7 purchase totals =	$639.97		$700.4553	$700.46	$700.45	$700.60