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	$250.48	7.543%	$269.3737	$269.37	$269.35	$269.40
Purchase #2	$29.58	9.491%	$32.3874	$32.39	$32.40	$32.40
Purchase #3	$199.93	11.329%	$222.5801	$222.58	$222.60	$222.60
Purchase #4	$15.35	12.404%	$17.254	$17.25	$17.25	$17.30
Purchase #5	$205.78	10.315%	$227.0062	$227.01	$227.00	$227.00
Purchase #6	$139.98	11.259%	$155.7403	$155.74	$155.75	$155.70
Purchase #7	$150.76	3.855%	$156.5718	$156.57	$156.55	$156.60
7 purchase totals =	$991.86		$1,080.9135	$1,080.91	$1,080.90	$1,081.00