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	$213.48	9.127%	$232.9643	$232.96	$232.95	$233.00
Purchase #2	$222.79	9.265%	$243.4315	$243.43	$243.45	$243.40
Purchase #3	$98.60	11.721%	$110.1569	$110.16	$110.15	$110.20
Purchase #4	$214.48	3.657%	$222.3235	$222.32	$222.30	$222.30
Purchase #5	$15.59	9.114%	$17.0109	$17.01	$17.00	$17.00
Purchase #6	$12.89	11.677%	$14.3952	$14.40	$14.40	$14.40
Purchase #7	$127.89	7.766%	$137.8219	$137.82	$137.80	$137.80
7 purchase totals =	$905.72		$978.1042	$978.10	$978.05	$978.10