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	$156.81	4.324%	$163.5905	$163.59	$163.60	$163.60
Purchase #2	$91.84	3.776%	$95.3079	$95.31	$95.30	$95.30
Purchase #3	$233.95	3.661%	$242.5149	$242.51	$242.50	$242.50
Purchase #4	$174.45	9.700%	$191.3717	$191.37	$191.35	$191.40
Purchase #5	$7.78	6.267%	$8.2676	$8.27	$8.25	$8.30
Purchase #6	$78.94	13.785%	$89.8219	$89.82	$89.80	$89.80
Purchase #7	$208.54	5.648%	$220.3183	$220.32	$220.30	$220.30
7 purchase totals =	$952.31		$1,011.1928	$1,011.19	$1,011.10	$1,011.20