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	$41.85	3.468%	$43.3014	$43.30	$43.30	$43.30
Purchase #2	$58.76	6.433%	$62.54	$62.54	$62.55	$62.50
Purchase #3	$31.51	9.442%	$34.4852	$34.49	$34.50	$34.50
Purchase #4	$182.59	4.493%	$190.7938	$190.79	$190.80	$190.80
Purchase #5	$172.92	4.604%	$180.8812	$180.88	$180.90	$180.90
Purchase #6	$68.25	11.598%	$76.1656	$76.17	$76.15	$76.20
Purchase #7	$181.35	9.279%	$198.1775	$198.18	$198.20	$198.20
7 purchase totals =	$737.23		$786.3447	$786.35	$786.40	$786.40