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	$62.76	10.573%	$69.3956	$69.40	$69.40	$69.40
Purchase #2	$96.82	13.429%	$109.822	$109.82	$109.80	$109.80
Purchase #3	$169.54	10.185%	$186.8076	$186.81	$186.80	$186.80
Purchase #4	$129.61	5.684%	$136.977	$136.98	$137.00	$137.00
Purchase #5	$19.61	8.265%	$21.2308	$21.23	$21.25	$21.20
Purchase #6	$113.69	8.580%	$123.4446	$123.44	$123.45	$123.40
Purchase #7	$34.41	8.721%	$37.4109	$37.41	$37.40	$37.40
7 purchase totals =	$626.44		$685.0885	$685.09	$685.10	$685.00