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	$86.54	13.699%	$98.3951	$98.40	$98.40	$98.40
Purchase #2	$212.43	13.469%	$241.0422	$241.04	$241.05	$241.00
Purchase #3	$35.69	9.551%	$39.0988	$39.10	$39.10	$39.10
Purchase #4	$85.91	13.308%	$97.3429	$97.34	$97.35	$97.30
Purchase #5	$200.65	7.259%	$215.2152	$215.22	$215.20	$215.20
Purchase #6	$250.31	12.213%	$280.8804	$280.88	$280.90	$280.90
Purchase #7	$92.39	8.184%	$99.9512	$99.95	$99.95	$100.00
7 purchase totals =	$963.92		$1,071.9258	$1,071.93	$1,071.95	$1,071.90