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	$151.43	13.275%	$171.5323	$171.53	$171.55	$171.50
Purchase #2	$13.93	6.663%	$14.8582	$14.86	$14.85	$14.90
Purchase #3	$240.92	13.582%	$273.6418	$273.64	$273.65	$273.60
Purchase #4	$69.62	3.863%	$72.3094	$72.31	$72.30	$72.30
Purchase #5	$161.77	11.781%	$180.8281	$180.83	$180.85	$180.80
Purchase #6	$161.92	7.344%	$173.8114	$173.81	$173.80	$173.80
Purchase #7	$237.45	9.216%	$259.3334	$259.33	$259.35	$259.30
7 purchase totals =	$1,037.04		$1,146.3146	$1,146.31	$1,146.35	$1,146.20