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	$195.37	3.707%	$202.6124	$202.61	$202.60	$202.60
Purchase #2	$68.79	13.536%	$78.1014	$78.10	$78.10	$78.10
Purchase #3	$160.88	8.834%	$175.0921	$175.09	$175.10	$175.10
Purchase #4	$26.37	8.258%	$28.5476	$28.55	$28.55	$28.50
Purchase #5	$77.31	11.188%	$85.9594	$85.96	$85.95	$86.00
Purchase #6	$93.40	7.710%	$100.6011	$100.60	$100.60	$100.60
Purchase #7	$63.37	12.183%	$71.0904	$71.09	$71.10	$71.10
7 purchase totals =	$685.49		$742.0044	$742.00	$742.00	$742.00