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	$131.76	9.395%	$144.1389	$144.14	$144.15	$144.10
Purchase #2	$86.64	10.577%	$95.8039	$95.80	$95.80	$95.80
Purchase #3	$170.47	7.338%	$182.9791	$182.98	$183.00	$183.00
Purchase #4	$247.77	13.150%	$280.3518	$280.35	$280.35	$280.40
Purchase #5	$61.25	10.684%	$67.794	$67.79	$67.80	$67.80
Purchase #6	$168.83	11.155%	$187.663	$187.66	$187.65	$187.70
Purchase #7	$57.75	8.619%	$62.7275	$62.73	$62.75	$62.70
7 purchase totals =	$924.47		$1,021.4582	$1,021.45	$1,021.50	$1,021.50