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	$54.95	7.753%	$59.2103	$59.21	$59.20	$59.20
Purchase #2	$29.78	4.168%	$31.0212	$31.02	$31.00	$31.00
Purchase #3	$123.88	7.816%	$133.5625	$133.56	$133.55	$133.60
Purchase #4	$112.27	12.532%	$126.3397	$126.34	$126.35	$126.30
Purchase #5	$62.66	4.467%	$65.459	$65.46	$65.45	$65.50
Purchase #6	$34.55	6.563%	$36.8175	$36.82	$36.80	$36.80
Purchase #7	$34.55	4.349%	$36.0526	$36.05	$36.05	$36.10
7 purchase totals =	$452.64		$488.4628	$488.46	$488.40	$488.50