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	$228.94	11.543%	$255.3665	$255.37	$255.35	$255.40
Purchase #2	$114.27	13.349%	$129.5239	$129.52	$129.50	$129.50
Purchase #3	$197.69	12.653%	$222.7037	$222.70	$222.70	$222.70
Purchase #4	$203.83	5.330%	$214.6941	$214.69	$214.70	$214.70
Purchase #5	$142.38	5.705%	$150.5028	$150.50	$150.50	$150.50
Purchase #6	$36.54	10.156%	$40.251	$40.25	$40.25	$40.30
Purchase #7	$32.36	13.606%	$36.7629	$36.76	$36.75	$36.80
7 purchase totals =	$956.01		$1,049.8049	$1,049.79	$1,049.75	$1,049.90