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	$217.96	10.490%	$240.824	$240.82	$240.80	$240.80
Purchase #2	$156.69	9.796%	$172.0394	$172.04	$172.05	$172.00
Purchase #3	$205.29	10.174%	$226.1762	$226.18	$226.20	$226.20
Purchase #4	$249.53	12.226%	$280.0375	$280.04	$280.05	$280.00
Purchase #5	$68.91	3.620%	$71.4045	$71.40	$71.40	$71.40
Purchase #6	$64.92	12.698%	$73.1635	$73.16	$73.15	$73.20
Purchase #7	$21.31	6.586%	$22.7135	$22.71	$22.70	$22.70
7 purchase totals =	$984.61		$1,086.3586	$1,086.35	$1,086.35	$1,086.30