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	$208.66	6.645%	$222.5255	$222.53	$222.55	$222.50
Purchase #2	$54.49	8.624%	$59.1892	$59.19	$59.20	$59.20
Purchase #3	$5.82	8.390%	$6.3083	$6.31	$6.30	$6.30
Purchase #4	$114.69	10.696%	$126.9572	$126.96	$126.95	$127.00
Purchase #5	$173.48	6.199%	$184.234	$184.23	$184.25	$184.20
Purchase #6	$167.64	7.324%	$179.918	$179.92	$179.90	$179.90
Purchase #7	$149.78	6.738%	$159.8722	$159.87	$159.85	$159.90
7 purchase totals =	$874.56		$939.0044	$939.01	$939.00	$939.00