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	$114.76	10.159%	$126.4185	$126.42	$126.40	$126.40
Purchase #2	$97.29	3.192%	$100.3955	$100.40	$100.40	$100.40
Purchase #3	$129.42	10.657%	$143.2123	$143.21	$143.20	$143.20
Purchase #4	$184.64	6.643%	$196.9056	$196.91	$196.90	$196.90
Purchase #5	$202.35	10.761%	$224.1249	$224.12	$224.10	$224.10
Purchase #6	$102.29	10.356%	$112.8832	$112.88	$112.90	$112.90
Purchase #7	$55.27	8.306%	$59.8607	$59.86	$59.85	$59.90
7 purchase totals =	$886.02		$963.8007	$963.80	$963.75	$963.80