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	$247.77	3.180%	$255.6491	$255.65	$255.65	$255.60
Purchase #2	$27.72	13.206%	$31.3807	$31.38	$31.40	$31.40
Purchase #3	$117.54	11.213%	$130.7198	$130.72	$130.70	$130.70
Purchase #4	$90.97	3.863%	$94.4842	$94.48	$94.50	$94.50
Purchase #5	$120.87	9.587%	$132.4578	$132.46	$132.45	$132.50
Purchase #6	$138.41	10.134%	$152.4365	$152.44	$152.45	$152.40
Purchase #7	$187.73	13.321%	$212.7375	$212.74	$212.75	$212.70
7 purchase totals =	$931.01		$1,009.8656	$1,009.87	$1,009.90	$1,009.80