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	$201.69	5.846%	$213.4808	$213.48	$213.50	$213.50
Purchase #2	$167.55	11.135%	$186.2067	$186.21	$186.20	$186.20
Purchase #3	$102.48	9.175%	$111.8825	$111.88	$111.90	$111.90
Purchase #4	$249.32	9.773%	$273.686	$273.69	$273.70	$273.70
Purchase #5	$136.28	11.619%	$152.1144	$152.11	$152.10	$152.10
Purchase #6	$100.78	4.158%	$104.9704	$104.97	$104.95	$105.00
Purchase #7	$67.34	10.652%	$74.5131	$74.51	$74.50	$74.50
7 purchase totals =	$1,025.44		$1,116.8539	$1,116.85	$1,116.85	$1,116.90