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	$75.92	13.123%	$85.883	$85.88	$85.90	$85.90
Purchase #2	$88.50	13.431%	$100.3864	$100.39	$100.40	$100.40
Purchase #3	$231.52	11.495%	$258.1332	$258.13	$258.15	$258.10
Purchase #4	$141.26	10.831%	$156.5599	$156.56	$156.55	$156.60
Purchase #5	$160.80	13.382%	$182.3183	$182.32	$182.30	$182.30
Purchase #6	$236.69	12.230%	$265.6372	$265.64	$265.65	$265.60
Purchase #7	$231.68	12.183%	$259.9056	$259.91	$259.90	$259.90
7 purchase totals =	$1,166.37		$1,308.8236	$1,308.83	$1,308.85	$1,308.80