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	$88.80	13.512%	$100.7987	$100.80	$100.80	$100.80
Purchase #2	$92.38	6.305%	$98.2046	$98.20	$98.20	$98.20
Purchase #3	$119.25	10.166%	$131.373	$131.37	$131.35	$131.40
Purchase #4	$7.26	4.661%	$7.5984	$7.60	$7.60	$7.60
Purchase #5	$100.74	8.385%	$109.187	$109.19	$109.20	$109.20
Purchase #6	$142.83	9.789%	$156.8116	$156.81	$156.80	$156.80
Purchase #7	$87.44	4.722%	$91.5689	$91.57	$91.55	$91.60
7 purchase totals =	$638.70		$695.5422	$695.54	$695.50	$695.60