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	$226.68	13.612%	$257.5357	$257.54	$257.55	$257.50
Purchase #2	$236.93	7.785%	$255.375	$255.38	$255.40	$255.40
Purchase #3	$46.44	4.299%	$48.4365	$48.44	$48.45	$48.40
Purchase #4	$52.31	13.715%	$59.4843	$59.48	$59.50	$59.50
Purchase #5	$232.54	13.843%	$264.7305	$264.73	$264.75	$264.70
Purchase #6	$247.71	5.578%	$261.5273	$261.53	$261.55	$261.50
Purchase #7	$15.83	9.139%	$17.2767	$17.28	$17.30	$17.30
7 purchase totals =	$1,058.44		$1,164.3660	$1,164.38	$1,164.50	$1,164.30