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	$228.55	13.439%	$259.2648	$259.26	$259.25	$259.30
Purchase #2	$127.89	11.342%	$142.3953	$142.40	$142.40	$142.40
Purchase #3	$91.62	11.417%	$102.0803	$102.08	$102.10	$102.10
Purchase #4	$178.57	11.600%	$199.2841	$199.28	$199.30	$199.30
Purchase #5	$55.64	7.240%	$59.6683	$59.67	$59.65	$59.70
Purchase #6	$25.75	8.453%	$27.9266	$27.93	$27.95	$27.90
Purchase #7	$200.31	7.365%	$215.0628	$215.06	$215.05	$215.10
7 purchase totals =	$908.33		$1,005.6822	$1,005.68	$1,005.70	$1,005.80