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	$101.48	9.734%	$111.3581	$111.36	$111.35	$111.40
Purchase #2	$158.71	12.524%	$178.5868	$178.59	$178.60	$178.60
Purchase #3	$134.81	9.629%	$147.7909	$147.79	$147.80	$147.80
Purchase #4	$179.94	4.757%	$188.4997	$188.50	$188.50	$188.50
Purchase #5	$160.78	5.381%	$169.4316	$169.43	$169.45	$169.40
Purchase #6	$92.92	5.381%	$97.92	$97.92	$97.90	$97.90
Purchase #7	$109.63	6.618%	$116.8853	$116.89	$116.90	$116.90
7 purchase totals =	$938.27		$1,010.4724	$1,010.48	$1,010.50	$1,010.50