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	$31.36	3.451%	$32.4422	$32.44	$32.45	$32.40
Purchase #2	$61.32	4.596%	$64.1383	$64.14	$64.15	$64.10
Purchase #3	$9.81	3.350%	$10.1386	$10.14	$10.15	$10.10
Purchase #4	$40.89	7.477%	$43.9473	$43.95	$43.95	$43.90
Purchase #5	$239.67	6.859%	$256.109	$256.11	$256.10	$256.10
Purchase #6	$162.48	3.218%	$167.7086	$167.71	$167.70	$167.70
Purchase #7	$172.95	12.661%	$194.8472	$194.85	$194.85	$194.80
7 purchase totals =	$718.48		$769.3312	$769.34	$769.35	$769.10