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	$189.42	10.341%	$209.0079	$209.01	$209.00	$209.00
Purchase #2	$234.98	7.140%	$251.7576	$251.76	$251.75	$251.80
Purchase #3	$185.89	5.854%	$196.772	$196.77	$196.75	$196.80
Purchase #4	$52.55	13.203%	$59.4882	$59.49	$59.50	$59.50
Purchase #5	$32.98	9.290%	$36.0438	$36.04	$36.05	$36.00
Purchase #6	$102.78	9.432%	$112.4742	$112.47	$112.45	$112.50
Purchase #7	$203.29	5.241%	$213.9444	$213.94	$213.95	$213.90
7 purchase totals =	$1,001.89		$1,079.4881	$1,079.48	$1,079.45	$1,079.50