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	$144.94	3.869%	$150.5477	$150.55	$150.55	$150.50
Purchase #2	$82.39	12.458%	$92.6541	$92.65	$92.65	$92.70
Purchase #3	$168.27	10.738%	$186.3388	$186.34	$186.35	$186.30
Purchase #4	$115.74	5.842%	$122.5015	$122.50	$122.50	$122.50
Purchase #5	$174.37	12.404%	$195.9989	$196.00	$196.00	$196.00
Purchase #6	$203.63	9.722%	$223.4269	$223.43	$223.45	$223.40
Purchase #7	$169.35	3.542%	$175.3484	$175.35	$175.35	$175.30
7 purchase totals =	$1,058.69		$1,146.8163	$1,146.82	$1,146.85	$1,146.70