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	$213.97	8.366%	$231.8707	$231.87	$231.85	$231.90
Purchase #2	$94.88	7.787%	$102.2683	$102.27	$102.25	$102.30
Purchase #3	$113.95	12.260%	$127.9203	$127.92	$127.90	$127.90
Purchase #4	$94.29	4.285%	$98.3303	$98.33	$98.35	$98.30
Purchase #5	$138.34	8.592%	$150.2262	$150.23	$150.25	$150.20
Purchase #6	$180.46	8.848%	$196.4271	$196.43	$196.45	$196.40
Purchase #7	$71.85	6.470%	$76.4987	$76.50	$76.50	$76.50
7 purchase totals =	$907.74		$983.5416	$983.55	$983.55	$983.50