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	$47.94	8.365%	$51.9502	$51.95	$51.95	$52.00
Purchase #2	$102.50	10.137%	$112.8904	$112.89	$112.90	$112.90
Purchase #3	$234.95	12.338%	$263.9381	$263.94	$263.95	$263.90
Purchase #4	$178.97	5.148%	$188.1834	$188.18	$188.20	$188.20
Purchase #5	$41.89	9.672%	$45.9416	$45.94	$45.95	$45.90
Purchase #6	$179.54	10.434%	$198.2732	$198.27	$198.25	$198.30
Purchase #7	$203.54	7.457%	$218.718	$218.72	$218.70	$218.70
7 purchase totals =	$989.33		$1,079.8949	$1,079.89	$1,079.90	$1,079.90