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	$43.36	11.804%	$48.4782	$48.48	$48.50	$48.50
Purchase #2	$158.75	6.254%	$168.6782	$168.68	$168.70	$168.70
Purchase #3	$250.92	9.119%	$273.8014	$273.80	$273.80	$273.80
Purchase #4	$131.97	4.454%	$137.8479	$137.85	$137.85	$137.80
Purchase #5	$46.80	10.803%	$51.8558	$51.86	$51.85	$51.90
Purchase #6	$244.76	11.429%	$272.7336	$272.73	$272.75	$272.70
Purchase #7	$234.74	9.256%	$256.4675	$256.47	$256.45	$256.50
7 purchase totals =	$1,111.30		$1,209.8626	$1,209.87	$1,209.90	$1,209.90