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	$128.85	9.443%	$141.0173	$141.02	$141.00	$141.00
Purchase #2	$76.37	12.719%	$86.0835	$86.08	$86.10	$86.10
Purchase #3	$199.44	9.528%	$218.4426	$218.44	$218.45	$218.40
Purchase #4	$11.95	13.160%	$13.5226	$13.52	$13.50	$13.50
Purchase #5	$94.49	5.303%	$99.5008	$99.50	$99.50	$99.50
Purchase #6	$109.65	13.516%	$124.4703	$124.47	$124.45	$124.50
Purchase #7	$154.76	3.782%	$160.613	$160.61	$160.60	$160.60
7 purchase totals =	$775.51		$843.6501	$843.64	$843.60	$843.60