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	$51.34	6.441%	$54.6468	$54.65	$54.65	$54.60
Purchase #2	$64.85	3.401%	$67.0555	$67.06	$67.05	$67.10
Purchase #3	$232.61	11.342%	$258.9926	$258.99	$259.00	$259.00
Purchase #4	$92.97	11.787%	$103.9284	$103.93	$103.95	$103.90
Purchase #5	$233.59	9.399%	$255.5451	$255.55	$255.55	$255.50
Purchase #6	$42.56	10.477%	$47.019	$47.02	$47.00	$47.00
Purchase #7	$213.49	10.387%	$235.6652	$235.67	$235.65	$235.70
7 purchase totals =	$931.41		$1,022.8526	$1,022.87	$1,022.85	$1,022.80