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	$200.65	5.129%	$210.9413	$210.94	$210.95	$210.90
Purchase #2	$199.30	8.162%	$215.5669	$215.57	$215.55	$215.60
Purchase #3	$174.83	9.784%	$191.9354	$191.94	$191.95	$191.90
Purchase #4	$77.98	6.452%	$83.0113	$83.01	$83.00	$83.00
Purchase #5	$194.47	11.248%	$216.344	$216.34	$216.35	$216.30
Purchase #6	$129.44	11.234%	$143.9813	$143.98	$144.00	$144.00
Purchase #7	$61.70	13.574%	$70.0752	$70.08	$70.10	$70.10
7 purchase totals =	$1,038.37		$1,131.8554	$1,131.86	$1,131.90	$1,131.80