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	$179.34	10.691%	$198.5132	$198.51	$198.50	$198.50
Purchase #2	$50.77	6.260%	$53.9482	$53.95	$53.95	$53.90
Purchase #3	$59.80	12.413%	$67.223	$67.22	$67.20	$67.20
Purchase #4	$79.68	8.147%	$86.1715	$86.17	$86.15	$86.20
Purchase #5	$114.94	3.117%	$118.5227	$118.52	$118.50	$118.50
Purchase #6	$215.86	11.362%	$240.386	$240.39	$240.40	$240.40
Purchase #7	$130.83	4.775%	$137.0771	$137.08	$137.10	$137.10
7 purchase totals =	$831.22		$901.8417	$901.84	$901.80	$901.80