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	$228.38	10.790%	$253.0222	$253.02	$253.00	$253.00
Purchase #2	$226.97	11.628%	$253.3621	$253.36	$253.35	$253.40
Purchase #3	$174.40	12.302%	$195.8547	$195.85	$195.85	$195.90
Purchase #4	$74.56	5.360%	$78.5564	$78.56	$78.55	$78.60
Purchase #5	$237.67	7.660%	$255.8755	$255.88	$255.90	$255.90
Purchase #6	$145.65	8.711%	$158.3376	$158.34	$158.35	$158.30
Purchase #7	$155.29	5.831%	$164.345	$164.35	$164.35	$164.30
7 purchase totals =	$1,242.92		$1,359.3535	$1,359.36	$1,359.35	$1,359.40