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	$213.41	8.618%	$231.8017	$231.80	$231.80	$231.80
Purchase #2	$228.82	4.688%	$239.5471	$239.55	$239.55	$239.50
Purchase #3	$85.85	11.443%	$95.6738	$95.67	$95.65	$95.70
Purchase #4	$180.61	8.161%	$195.3496	$195.35	$195.35	$195.30
Purchase #5	$35.57	8.530%	$38.6041	$38.60	$38.60	$38.60
Purchase #6	$182.59	7.396%	$196.0944	$196.09	$196.10	$196.10
Purchase #7	$126.37	4.370%	$131.8924	$131.89	$131.90	$131.90
7 purchase totals =	$1,053.22		$1,128.9631	$1,128.95	$1,128.95	$1,128.90