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	$203.76	9.207%	$222.5202	$222.52	$222.50	$222.50
Purchase #2	$183.76	7.299%	$197.1726	$197.17	$197.15	$197.20
Purchase #3	$45.61	6.613%	$48.6262	$48.63	$48.65	$48.60
Purchase #4	$32.82	12.619%	$36.9616	$36.96	$36.95	$37.00
Purchase #5	$128.43	11.762%	$143.5359	$143.54	$143.55	$143.50
Purchase #6	$163.59	10.109%	$180.1273	$180.13	$180.15	$180.10
Purchase #7	$203.43	7.396%	$218.4757	$218.48	$218.50	$218.50
7 purchase totals =	$961.40		$1,047.4195	$1,047.43	$1,047.45	$1,047.40