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	$175.50	10.781%	$194.4207	$194.42	$194.40	$194.40
Purchase #2	$70.87	10.671%	$78.4325	$78.43	$78.45	$78.40
Purchase #3	$136.88	3.459%	$141.6147	$141.61	$141.60	$141.60
Purchase #4	$109.96	5.795%	$116.3322	$116.33	$116.35	$116.30
Purchase #5	$89.60	9.665%	$98.2598	$98.26	$98.25	$98.30
Purchase #6	$217.78	3.224%	$224.8012	$224.80	$224.80	$224.80
Purchase #7	$56.25	5.527%	$59.3589	$59.36	$59.35	$59.40
7 purchase totals =	$856.84		$913.2200	$913.21	$913.20	$913.20