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	$231.35	12.535%	$260.3497	$260.35	$260.35	$260.30
Purchase #2	$147.88	4.355%	$154.3202	$154.32	$154.30	$154.30
Purchase #3	$247.40	4.701%	$259.0303	$259.03	$259.05	$259.00
Purchase #4	$126.90	9.548%	$139.0164	$139.02	$139.00	$139.00
Purchase #5	$80.65	11.317%	$89.7772	$89.78	$89.80	$89.80
Purchase #6	$23.83	6.195%	$25.3063	$25.31	$25.30	$25.30
Purchase #7	$247.88	8.430%	$268.7763	$268.78	$268.80	$268.80
7 purchase totals =	$1,105.89		$1,196.5764	$1,196.59	$1,196.60	$1,196.50