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	$239.38	8.673%	$260.1414	$260.14	$260.15	$260.10
Purchase #2	$233.32	7.543%	$250.9193	$250.92	$250.90	$250.90
Purchase #3	$188.64	13.723%	$214.5271	$214.53	$214.55	$214.50
Purchase #4	$50.25	13.687%	$57.1277	$57.13	$57.15	$57.10
Purchase #5	$171.87	11.390%	$191.446	$191.45	$191.45	$191.40
Purchase #6	$100.59	13.815%	$114.4865	$114.49	$114.50	$114.50
Purchase #7	$182.40	7.685%	$196.4174	$196.42	$196.40	$196.40
7 purchase totals =	$1,166.45		$1,285.0654	$1,285.08	$1,285.10	$1,284.90