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	$137.58	11.255%	$153.0646	$153.06	$153.05	$153.10
Purchase #2	$137.58	7.496%	$147.893	$147.89	$147.90	$147.90
Purchase #3	$112.77	12.558%	$126.9317	$126.93	$126.95	$126.90
Purchase #4	$249.46	4.184%	$259.8974	$259.90	$259.90	$259.90
Purchase #5	$105.87	3.448%	$109.5204	$109.52	$109.50	$109.50
Purchase #6	$84.47	12.847%	$95.3219	$95.32	$95.30	$95.30
Purchase #7	$132.78	13.197%	$150.303	$150.30	$150.30	$150.30
7 purchase totals =	$960.51		$1,042.9320	$1,042.92	$1,042.90	$1,042.90