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	$118.73	10.809%	$131.5635	$131.56	$131.55	$131.60
Purchase #2	$200.67	10.218%	$221.1745	$221.17	$221.15	$221.20
Purchase #3	$34.91	13.826%	$39.7367	$39.74	$39.75	$39.70
Purchase #4	$104.95	13.709%	$119.3376	$119.34	$119.35	$119.30
Purchase #5	$101.30	10.520%	$111.9568	$111.96	$111.95	$112.00
Purchase #6	$55.35	11.277%	$61.5918	$61.59	$61.60	$61.60
Purchase #7	$238.54	11.354%	$265.6238	$265.62	$265.60	$265.60
7 purchase totals =	$854.45		$950.9847	$950.98	$950.95	$951.00