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	$13.98	13.377%	$15.8501	$15.85	$15.85	$15.90
Purchase #2	$232.42	10.259%	$256.264	$256.26	$256.25	$256.30
Purchase #3	$152.63	10.296%	$168.3448	$168.34	$168.35	$168.30
Purchase #4	$187.43	3.844%	$194.6348	$194.63	$194.65	$194.60
Purchase #5	$148.90	7.850%	$160.5887	$160.59	$160.60	$160.60
Purchase #6	$33.67	10.761%	$37.2932	$37.29	$37.30	$37.30
Purchase #7	$185.53	8.142%	$200.6359	$200.64	$200.65	$200.60
7 purchase totals =	$954.56		$1,033.6115	$1,033.60	$1,033.65	$1,033.60