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	$52.64	12.358%	$59.1453	$59.15	$59.15	$59.10
Purchase #2	$78.50	4.870%	$82.323	$82.32	$82.30	$82.30
Purchase #3	$29.43	8.278%	$31.8662	$31.87	$31.85	$31.90
Purchase #4	$209.96	3.674%	$217.6739	$217.67	$217.65	$217.70
Purchase #5	$207.30	8.694%	$225.3227	$225.32	$225.30	$225.30
Purchase #6	$199.57	5.432%	$210.4106	$210.41	$210.40	$210.40
Purchase #7	$91.72	3.424%	$94.8605	$94.86	$94.85	$94.90
7 purchase totals =	$869.12		$921.6022	$921.60	$921.50	$921.60