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	$69.76	4.621%	$72.9836	$72.98	$73.00	$73.00
Purchase #2	$117.32	8.283%	$127.0376	$127.04	$127.05	$127.00
Purchase #3	$213.81	3.629%	$221.5692	$221.57	$221.55	$221.60
Purchase #4	$38.41	13.870%	$43.7375	$43.74	$43.75	$43.70
Purchase #5	$174.38	12.660%	$196.4565	$196.46	$196.45	$196.50
Purchase #6	$196.42	13.248%	$222.4417	$222.44	$222.45	$222.40
Purchase #7	$60.71	4.118%	$63.21	$63.21	$63.20	$63.20
7 purchase totals =	$870.81		$947.4361	$947.44	$947.45	$947.40