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	$23.42	4.471%	$24.4671	$24.47	$24.45	$24.50
Purchase #2	$200.94	5.366%	$211.7224	$211.72	$211.70	$211.70
Purchase #3	$98.53	11.430%	$109.792	$109.79	$109.80	$109.80
Purchase #4	$61.51	10.124%	$67.7373	$67.74	$67.75	$67.70
Purchase #5	$229.84	11.686%	$256.6991	$256.70	$256.70	$256.70
Purchase #6	$233.82	9.438%	$255.8879	$255.89	$255.90	$255.90
Purchase #7	$246.31	3.437%	$254.7757	$254.78	$254.80	$254.80
7 purchase totals =	$1,094.37		$1,181.0815	$1,181.09	$1,181.10	$1,181.10