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	$41.47	12.437%	$46.6276	$46.63	$46.65	$46.60
Purchase #2	$169.80	9.287%	$185.5693	$185.57	$185.55	$185.60
Purchase #3	$83.47	8.334%	$90.4264	$90.43	$90.45	$90.40
Purchase #4	$20.89	3.605%	$21.6431	$21.64	$21.65	$21.60
Purchase #5	$207.82	9.678%	$227.9328	$227.93	$227.95	$227.90
Purchase #6	$219.85	6.121%	$233.307	$233.31	$233.30	$233.30
Purchase #7	$93.46	7.299%	$100.2816	$100.28	$100.30	$100.30
7 purchase totals =	$836.76		$905.7878	$905.79	$905.85	$905.70