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	$71.81	9.501%	$78.6327	$78.63	$78.65	$78.60
Purchase #2	$227.80	5.585%	$240.5226	$240.52	$240.50	$240.50
Purchase #3	$200.37	13.208%	$226.8349	$226.83	$226.85	$226.80
Purchase #4	$129.77	10.549%	$143.4594	$143.46	$143.45	$143.50
Purchase #5	$31.91	11.447%	$35.5627	$35.56	$35.55	$35.60
Purchase #6	$188.25	6.533%	$200.5484	$200.55	$200.55	$200.50
Purchase #7	$215.83	5.308%	$227.2863	$227.29	$227.30	$227.30
7 purchase totals =	$1,065.74		$1,152.8470	$1,152.84	$1,152.85	$1,152.80