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	$61.33	8.754%	$66.6988	$66.70	$66.70	$66.70
Purchase #2	$175.25	12.223%	$196.6708	$196.67	$196.65	$196.70
Purchase #3	$96.65	4.359%	$100.863	$100.86	$100.85	$100.90
Purchase #4	$142.90	8.224%	$154.6521	$154.65	$154.65	$154.70
Purchase #5	$17.89	10.572%	$19.7813	$19.78	$19.80	$19.80
Purchase #6	$209.39	4.339%	$218.4754	$218.48	$218.50	$218.50
Purchase #7	$34.89	10.469%	$38.5426	$38.54	$38.55	$38.50
7 purchase totals =	$738.30		$795.6840	$795.68	$795.70	$795.80