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	$113.75	10.852%	$126.0942	$126.09	$126.10	$126.10
Purchase #2	$191.94	3.470%	$198.6003	$198.60	$198.60	$198.60
Purchase #3	$246.82	7.515%	$265.3685	$265.37	$265.35	$265.40
Purchase #4	$76.38	11.750%	$85.3547	$85.35	$85.35	$85.40
Purchase #5	$39.95	8.274%	$43.2555	$43.26	$43.25	$43.30
Purchase #6	$86.66	4.621%	$90.6646	$90.66	$90.65	$90.70
Purchase #7	$205.34	5.809%	$217.2682	$217.27	$217.25	$217.30
7 purchase totals =	$960.84		$1,026.6060	$1,026.60	$1,026.55	$1,026.80