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	$98.35	13.304%	$111.4345	$111.43	$111.45	$111.40
Purchase #2	$189.50	13.747%	$215.5506	$215.55	$215.55	$215.60
Purchase #3	$68.29	5.438%	$72.0036	$72.00	$72.00	$72.00
Purchase #4	$208.31	10.132%	$229.416	$229.42	$229.40	$229.40
Purchase #5	$179.61	10.615%	$198.6756	$198.68	$198.70	$198.70
Purchase #6	$28.62	9.777%	$31.4182	$31.42	$31.40	$31.40
Purchase #7	$217.36	6.596%	$231.6971	$231.70	$231.70	$231.70
7 purchase totals =	$990.04		$1,090.1956	$1,090.20	$1,090.20	$1,090.20