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	$205.69	3.821%	$213.5494	$213.55	$213.55	$213.50
Purchase #2	$148.38	5.729%	$156.8807	$156.88	$156.90	$156.90
Purchase #3	$43.27	8.656%	$47.0155	$47.02	$47.00	$47.00
Purchase #4	$135.82	8.125%	$146.8554	$146.86	$146.85	$146.90
Purchase #5	$238.53	7.122%	$255.5181	$255.52	$255.50	$255.50
Purchase #6	$72.84	13.252%	$82.4928	$82.49	$82.50	$82.50
Purchase #7	$135.93	10.724%	$150.5071	$150.51	$150.50	$150.50
7 purchase totals =	$980.46		$1,052.8190	$1,052.83	$1,052.80	$1,052.80