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	$185.53	6.327%	$197.2685	$197.27	$197.25	$197.30
Purchase #2	$250.86	3.479%	$259.5874	$259.59	$259.60	$259.60
Purchase #3	$148.27	13.203%	$167.8461	$167.85	$167.85	$167.80
Purchase #4	$63.96	13.320%	$72.4795	$72.48	$72.50	$72.50
Purchase #5	$223.41	3.598%	$231.4483	$231.45	$231.45	$231.40
Purchase #6	$34.61	13.603%	$39.318	$39.32	$39.30	$39.30
Purchase #7	$118.46	3.602%	$122.7269	$122.73	$122.75	$122.70
7 purchase totals =	$1,025.10		$1,090.6747	$1,090.69	$1,090.70	$1,090.60