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	$134.84	3.383%	$139.4016	$139.40	$139.40	$139.40
Purchase #2	$13.97	6.264%	$14.8451	$14.85	$14.85	$14.80
Purchase #3	$59.80	7.717%	$64.4148	$64.41	$64.40	$64.40
Purchase #4	$194.35	12.345%	$218.3425	$218.34	$218.35	$218.30
Purchase #5	$139.50	10.168%	$153.6844	$153.68	$153.70	$153.70
Purchase #6	$231.86	10.752%	$256.7896	$256.79	$256.80	$256.80
Purchase #7	$90.71	10.772%	$100.4813	$100.48	$100.50	$100.50
7 purchase totals =	$865.03		$947.9593	$947.95	$948.00	$947.90