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	$82.89	9.228%	$90.5391	$90.54	$90.55	$90.50
Purchase #2	$24.98	9.828%	$27.435	$27.44	$27.45	$27.40
Purchase #3	$147.37	7.410%	$158.2901	$158.29	$158.30	$158.30
Purchase #4	$202.74	8.874%	$220.7311	$220.73	$220.75	$220.70
Purchase #5	$204.71	10.330%	$225.8565	$225.86	$225.85	$225.90
Purchase #6	$132.57	11.413%	$147.7002	$147.70	$147.70	$147.70
Purchase #7	$244.74	12.308%	$274.8626	$274.86	$274.85	$274.90
7 purchase totals =	$1,040.00		$1,145.4146	$1,145.42	$1,145.45	$1,145.40