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	$181.65	6.458%	$193.381	$193.38	$193.40	$193.40
Purchase #2	$232.95	3.659%	$241.4736	$241.47	$241.45	$241.50
Purchase #3	$216.98	8.256%	$234.8939	$234.89	$234.90	$234.90
Purchase #4	$213.84	12.569%	$240.7175	$240.72	$240.70	$240.70
Purchase #5	$80.69	11.348%	$89.8467	$89.85	$89.85	$89.80
Purchase #6	$238.29	6.402%	$253.5453	$253.55	$253.55	$253.50
Purchase #7	$218.66	12.240%	$245.424	$245.42	$245.40	$245.40
7 purchase totals =	$1,383.06		$1,499.2820	$1,499.28	$1,499.25	$1,499.20