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	$101.35	10.238%	$111.7262	$111.73	$111.75	$111.70
Purchase #2	$191.90	8.258%	$207.7471	$207.75	$207.75	$207.70
Purchase #3	$82.32	11.386%	$91.693	$91.69	$91.70	$91.70
Purchase #4	$97.79	4.259%	$101.9549	$101.95	$101.95	$102.00
Purchase #5	$18.83	7.325%	$20.2093	$20.21	$20.20	$20.20
Purchase #6	$49.81	12.475%	$56.0238	$56.02	$56.00	$56.00
Purchase #7	$84.96	5.334%	$89.4918	$89.49	$89.50	$89.50
7 purchase totals =	$626.96		$678.8461	$678.84	$678.85	$678.80