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	$102.46	8.570%	$111.2408	$111.24	$111.25	$111.20
Purchase #2	$227.74	4.724%	$238.4984	$238.50	$238.50	$238.50
Purchase #3	$189.33	5.374%	$199.5046	$199.50	$199.50	$199.50
Purchase #4	$63.36	13.530%	$71.9326	$71.93	$71.95	$71.90
Purchase #5	$25.35	8.550%	$27.5174	$27.52	$27.50	$27.50
Purchase #6	$170.46	9.393%	$186.4713	$186.47	$186.45	$186.50
Purchase #7	$232.30	5.548%	$245.188	$245.19	$245.20	$245.20
7 purchase totals =	$1,011.00		$1,080.3531	$1,080.35	$1,080.35	$1,080.30