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	$41.30	6.366%	$43.9292	$43.93	$43.95	$43.90
Purchase #2	$209.83	11.819%	$234.6298	$234.63	$234.65	$234.60
Purchase #3	$222.74	10.480%	$246.0832	$246.08	$246.10	$246.10
Purchase #4	$45.52	9.573%	$49.8776	$49.88	$49.90	$49.90
Purchase #5	$249.62	4.719%	$261.3996	$261.40	$261.40	$261.40
Purchase #6	$41.60	3.168%	$42.9179	$42.92	$42.90	$42.90
Purchase #7	$117.61	6.198%	$124.8995	$124.90	$124.90	$124.90
7 purchase totals =	$928.22		$1,003.7368	$1,003.74	$1,003.80	$1,003.70