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	$160.32	8.604%	$174.1139	$174.11	$174.10	$174.10
Purchase #2	$144.80	3.637%	$150.0664	$150.07	$150.05	$150.10
Purchase #3	$228.94	11.377%	$254.9865	$254.99	$255.00	$255.00
Purchase #4	$230.56	4.202%	$240.2481	$240.25	$240.25	$240.20
Purchase #5	$106.42	12.154%	$119.3543	$119.35	$119.35	$119.40
Purchase #6	$37.47	7.378%	$40.2345	$40.23	$40.25	$40.20
Purchase #7	$75.41	9.166%	$82.3221	$82.32	$82.30	$82.30
7 purchase totals =	$983.92		$1,061.3258	$1,061.32	$1,061.30	$1,061.30