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	$133.66	13.239%	$151.3552	$151.36	$151.35	$151.40
Purchase #2	$97.64	6.351%	$103.8411	$103.84	$103.85	$103.80
Purchase #3	$246.29	3.817%	$255.6909	$255.69	$255.70	$255.70
Purchase #4	$211.72	8.859%	$230.4763	$230.48	$230.50	$230.50
Purchase #5	$143.81	8.634%	$156.2266	$156.23	$156.25	$156.20
Purchase #6	$90.93	11.813%	$101.6716	$101.67	$101.65	$101.70
Purchase #7	$98.43	11.445%	$109.6953	$109.70	$109.70	$109.70
7 purchase totals =	$1,022.48		$1,108.9570	$1,108.97	$1,109.00	$1,109.00