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	$247.63	8.610%	$268.9509	$268.95	$268.95	$269.00
Purchase #2	$75.43	10.347%	$83.2347	$83.23	$83.25	$83.20
Purchase #3	$63.90	13.310%	$72.4051	$72.41	$72.40	$72.40
Purchase #4	$92.64	6.719%	$98.8645	$98.86	$98.85	$98.90
Purchase #5	$200.47	3.528%	$207.5426	$207.54	$207.55	$207.50
Purchase #6	$235.65	10.292%	$259.9031	$259.90	$259.90	$259.90
Purchase #7	$23.71	7.571%	$25.5051	$25.51	$25.50	$25.50
7 purchase totals =	$939.43		$1,016.4060	$1,016.40	$1,016.40	$1,016.40