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	$89.38	9.581%	$97.9435	$97.94	$97.95	$97.90
Purchase #2	$19.84	8.617%	$21.5496	$21.55	$21.55	$21.50
Purchase #3	$209.42	11.667%	$233.853	$233.85	$233.85	$233.90
Purchase #4	$183.66	5.223%	$193.2526	$193.25	$193.25	$193.30
Purchase #5	$109.25	13.787%	$124.3123	$124.31	$124.30	$124.30
Purchase #6	$101.50	9.657%	$111.3019	$111.30	$111.30	$111.30
Purchase #7	$227.33	13.409%	$257.8127	$257.81	$257.80	$257.80
7 purchase totals =	$940.38		$1,040.0256	$1,040.01	$1,040.00	$1,040.00