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	$244.64	4.624%	$255.9522	$255.95	$255.95	$256.00
Purchase #2	$163.48	3.674%	$169.4863	$169.49	$169.50	$169.50
Purchase #3	$98.29	5.163%	$103.3647	$103.36	$103.35	$103.40
Purchase #4	$157.38	3.239%	$162.4775	$162.48	$162.50	$162.50
Purchase #5	$100.36	3.507%	$103.8796	$103.88	$103.90	$103.90
Purchase #6	$239.63	8.458%	$259.8979	$259.90	$259.90	$259.90
Purchase #7	$10.91	7.663%	$11.746	$11.75	$11.75	$11.70
7 purchase totals =	$1,014.69		$1,066.8042	$1,066.81	$1,066.85	$1,066.90