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	$90.99	3.669%	$94.3284	$94.33	$94.35	$94.30
Purchase #2	$15.41	3.183%	$15.9005	$15.90	$15.90	$15.90
Purchase #3	$124.48	13.685%	$141.5151	$141.52	$141.50	$141.50
Purchase #4	$215.53	3.261%	$222.5584	$222.56	$222.55	$222.60
Purchase #5	$172.40	3.722%	$178.8167	$178.82	$178.80	$178.80
Purchase #6	$185.35	12.428%	$208.3853	$208.39	$208.40	$208.40
Purchase #7	$106.31	6.683%	$113.4147	$113.41	$113.40	$113.40
7 purchase totals =	$910.47		$974.9191	$974.93	$974.90	$974.90