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	$94.69	8.782%	$103.0057	$103.01	$103.00	$103.00
Purchase #2	$133.88	12.226%	$150.2482	$150.25	$150.25	$150.20
Purchase #3	$203.93	11.670%	$227.7286	$227.73	$227.75	$227.70
Purchase #4	$80.69	13.441%	$91.5355	$91.54	$91.55	$91.50
Purchase #5	$74.89	3.673%	$77.6407	$77.64	$77.65	$77.60
Purchase #6	$151.77	8.360%	$164.458	$164.46	$164.45	$164.50
Purchase #7	$186.83	6.441%	$198.8637	$198.86	$198.85	$198.90
7 purchase totals =	$926.68		$1,013.4804	$1,013.49	$1,013.50	$1,013.40