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	$69.82	3.453%	$72.2309	$72.23	$72.25	$72.20
Purchase #2	$196.73	13.224%	$222.7456	$222.75	$222.75	$222.70
Purchase #3	$109.48	3.348%	$113.1454	$113.15	$113.15	$113.10
Purchase #4	$92.29	6.234%	$98.0434	$98.04	$98.05	$98.00
Purchase #5	$87.42	4.679%	$91.5104	$91.51	$91.50	$91.50
Purchase #6	$129.90	7.616%	$139.7932	$139.79	$139.80	$139.80
Purchase #7	$81.89	3.256%	$84.5563	$84.56	$84.55	$84.60
7 purchase totals =	$767.53		$822.0252	$822.03	$822.05	$821.90