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	$43.75	13.504%	$49.658	$49.66	$49.65	$49.70
Purchase #2	$18.63	9.377%	$20.3769	$20.38	$20.40	$20.40
Purchase #3	$213.29	5.716%	$225.4817	$225.48	$225.50	$225.50
Purchase #4	$31.45	6.591%	$33.5229	$33.52	$33.50	$33.50
Purchase #5	$191.36	7.626%	$205.9531	$205.95	$205.95	$206.00
Purchase #6	$150.53	12.180%	$168.8646	$168.86	$168.85	$168.90
Purchase #7	$83.54	4.109%	$86.9727	$86.97	$86.95	$87.00
7 purchase totals =	$732.55		$790.8299	$790.82	$790.80	$791.00