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	$96.63	9.642%	$105.9471	$105.95	$105.95	$105.90
Purchase #2	$74.61	13.298%	$84.5316	$84.53	$84.55	$84.50
Purchase #3	$217.89	7.529%	$234.2949	$234.29	$234.30	$234.30
Purchase #4	$203.46	10.368%	$224.5547	$224.55	$224.55	$224.60
Purchase #5	$208.91	6.678%	$222.861	$222.86	$222.85	$222.90
Purchase #6	$45.50	10.492%	$50.2739	$50.27	$50.25	$50.30
Purchase #7	$147.93	11.497%	$164.9375	$164.94	$164.95	$164.90
7 purchase totals =	$994.93		$1,087.4007	$1,087.39	$1,087.40	$1,087.40