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	$147.40	13.179%	$166.8258	$166.83	$166.85	$166.80
Purchase #2	$94.92	4.862%	$99.535	$99.54	$99.55	$99.50
Purchase #3	$73.45	9.647%	$80.5357	$80.54	$80.55	$80.50
Purchase #4	$15.89	12.321%	$17.8478	$17.85	$17.85	$17.80
Purchase #5	$237.65	13.871%	$270.6144	$270.61	$270.60	$270.60
Purchase #6	$160.38	12.657%	$180.6793	$180.68	$180.70	$180.70
Purchase #7	$123.74	3.652%	$128.259	$128.26	$128.25	$128.30
7 purchase totals =	$853.43		$944.2970	$944.31	$944.35	$944.20