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	$143.68	4.718%	$150.4588	$150.46	$150.45	$150.50
Purchase #2	$87.55	11.831%	$97.908	$97.91	$97.90	$97.90
Purchase #3	$221.52	6.262%	$235.3916	$235.39	$235.40	$235.40
Purchase #4	$141.68	6.802%	$151.3171	$151.32	$151.30	$151.30
Purchase #5	$50.50	7.299%	$54.186	$54.19	$54.20	$54.20
Purchase #6	$88.46	4.493%	$92.4345	$92.43	$92.45	$92.40
Purchase #7	$246.48	13.720%	$280.2971	$280.30	$280.30	$280.30
7 purchase totals =	$979.87		$1,061.9931	$1,062.00	$1,062.00	$1,062.00