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	$182.27	11.108%	$202.5166	$202.52	$202.50	$202.50
Purchase #2	$245.25	4.174%	$255.4867	$255.49	$255.50	$255.50
Purchase #3	$99.88	5.437%	$105.3105	$105.31	$105.30	$105.30
Purchase #4	$181.51	4.365%	$189.4329	$189.43	$189.45	$189.40
Purchase #5	$213.34	8.477%	$231.4248	$231.42	$231.40	$231.40
Purchase #6	$174.63	12.523%	$196.4989	$196.50	$196.50	$196.50
Purchase #7	$86.41	13.305%	$97.9069	$97.91	$97.90	$97.90
7 purchase totals =	$1,183.29		$1,278.5773	$1,278.58	$1,278.55	$1,278.50