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	$245.80	3.387%	$254.1252	$254.13	$254.15	$254.10
Purchase #2	$38.81	11.631%	$43.324	$43.32	$43.30	$43.30
Purchase #3	$108.73	9.515%	$119.0757	$119.08	$119.10	$119.10
Purchase #4	$82.58	10.106%	$90.9255	$90.93	$90.95	$90.90
Purchase #5	$210.36	13.573%	$238.9122	$238.91	$238.90	$238.90
Purchase #6	$33.52	9.642%	$36.752	$36.75	$36.75	$36.80
Purchase #7	$30.39	10.533%	$33.591	$33.59	$33.60	$33.60
7 purchase totals =	$750.19		$816.7056	$816.71	$816.75	$816.70