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	$93.31	3.684%	$96.7475	$96.75	$96.75	$96.70
Purchase #2	$63.96	3.552%	$66.2319	$66.23	$66.25	$66.20
Purchase #3	$12.95	3.626%	$13.4196	$13.42	$13.40	$13.40
Purchase #4	$33.50	13.148%	$37.9046	$37.90	$37.90	$37.90
Purchase #5	$59.47	12.587%	$66.9555	$66.96	$66.95	$67.00
Purchase #6	$116.84	12.492%	$131.4357	$131.44	$131.45	$131.40
Purchase #7	$194.78	12.597%	$219.3164	$219.32	$219.30	$219.30
7 purchase totals =	$574.81		$632.0112	$632.02	$632.00	$631.90