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	$129.50	3.813%	$134.4378	$134.44	$134.45	$134.40
Purchase #2	$114.31	8.108%	$123.5783	$123.58	$123.60	$123.60
Purchase #3	$250.92	9.389%	$274.4789	$274.48	$274.50	$274.50
Purchase #4	$217.99	12.675%	$245.6202	$245.62	$245.60	$245.60
Purchase #5	$186.77	5.142%	$196.3737	$196.37	$196.35	$196.40
Purchase #6	$70.58	12.606%	$79.4773	$79.48	$79.50	$79.50
Purchase #7	$126.64	3.467%	$131.0306	$131.03	$131.05	$131.00
7 purchase totals =	$1,096.71		$1,184.9968	$1,185.00	$1,185.05	$1,185.00