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	$153.78	9.516%	$168.4137	$168.41	$168.40	$168.40
Purchase #2	$82.87	4.681%	$86.7491	$86.75	$86.75	$86.70
Purchase #3	$157.86	13.539%	$179.2327	$179.23	$179.25	$179.20
Purchase #4	$227.35	9.492%	$248.9301	$248.93	$248.95	$248.90
Purchase #5	$34.60	8.138%	$37.4157	$37.42	$37.40	$37.40
Purchase #6	$152.30	5.410%	$160.5394	$160.54	$160.55	$160.50
Purchase #7	$67.76	12.868%	$76.4794	$76.48	$76.50	$76.50
7 purchase totals =	$876.52		$957.7601	$957.76	$957.80	$957.60