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	$218.56	3.740%	$226.7341	$226.73	$226.75	$226.70
Purchase #2	$61.25	7.633%	$65.9252	$65.93	$65.95	$65.90
Purchase #3	$200.53	12.169%	$224.9325	$224.93	$224.95	$224.90
Purchase #4	$42.55	5.339%	$44.8217	$44.82	$44.80	$44.80
Purchase #5	$178.70	11.377%	$199.0307	$199.03	$199.05	$199.00
Purchase #6	$88.35	12.602%	$99.4839	$99.48	$99.50	$99.50
Purchase #7	$53.81	11.299%	$59.89	$59.89	$59.90	$59.90
7 purchase totals =	$843.75		$920.8181	$920.81	$920.90	$920.70