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	$199.82	9.384%	$218.5711	$218.57	$218.55	$218.60
Purchase #2	$238.92	8.361%	$258.8961	$258.90	$258.90	$258.90
Purchase #3	$201.89	13.375%	$228.8928	$228.89	$228.90	$228.90
Purchase #4	$162.83	3.266%	$168.148	$168.15	$168.15	$168.10
Purchase #5	$77.39	3.621%	$80.1923	$80.19	$80.20	$80.20
Purchase #6	$231.39	4.350%	$241.4555	$241.46	$241.45	$241.50
Purchase #7	$214.32	8.178%	$231.8471	$231.85	$231.85	$231.80
7 purchase totals =	$1,326.56		$1,428.0029	$1,428.01	$1,428.00	$1,428.00