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	$127.50	3.229%	$131.617	$131.62	$131.60	$131.60
Purchase #2	$18.47	6.352%	$19.6432	$19.64	$19.65	$19.60
Purchase #3	$103.83	5.763%	$109.8137	$109.81	$109.80	$109.80
Purchase #4	$221.88	4.772%	$232.4681	$232.47	$232.45	$232.50
Purchase #5	$242.79	6.391%	$258.3067	$258.31	$258.30	$258.30
Purchase #6	$247.70	6.535%	$263.8872	$263.89	$263.90	$263.90
Purchase #7	$164.88	13.796%	$187.6268	$187.63	$187.65	$187.60
7 purchase totals =	$1,127.05		$1,203.3627	$1,203.37	$1,203.35	$1,203.30