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	$100.63	3.813%	$104.467	$104.47	$104.45	$104.50
Purchase #2	$56.70	12.678%	$63.8884	$63.89	$63.90	$63.90
Purchase #3	$141.37	11.266%	$157.2967	$157.30	$157.30	$157.30
Purchase #4	$18.69	12.125%	$20.9562	$20.96	$20.95	$21.00
Purchase #5	$117.65	13.471%	$133.4986	$133.50	$133.50	$133.50
Purchase #6	$92.56	7.450%	$99.4557	$99.46	$99.45	$99.50
Purchase #7	$169.82	10.152%	$187.0601	$187.06	$187.05	$187.10
7 purchase totals =	$697.42		$766.6227	$766.64	$766.60	$766.80