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	$59.34	13.195%	$67.1699	$67.17	$67.15	$67.20
Purchase #2	$210.43	8.233%	$227.7547	$227.75	$227.75	$227.80
Purchase #3	$89.33	5.698%	$94.42	$94.42	$94.40	$94.40
Purchase #4	$248.99	5.691%	$263.16	$263.16	$263.15	$263.20
Purchase #5	$90.77	13.390%	$102.9241	$102.92	$102.90	$102.90
Purchase #6	$82.78	12.139%	$92.8287	$92.83	$92.85	$92.80
Purchase #7	$143.63	13.823%	$163.484	$163.48	$163.50	$163.50
7 purchase totals =	$925.27		$1,011.7414	$1,011.73	$1,011.70	$1,011.80