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	$127.66	13.594%	$145.0141	$145.01	$145.00	$145.00
Purchase #2	$41.61	12.802%	$46.9369	$46.94	$46.95	$46.90
Purchase #3	$225.32	5.148%	$236.9195	$236.92	$236.90	$236.90
Purchase #4	$153.34	7.627%	$165.0352	$165.04	$165.05	$165.00
Purchase #5	$115.32	10.736%	$127.7008	$127.70	$127.70	$127.70
Purchase #6	$194.85	9.706%	$213.7621	$213.76	$213.75	$213.80
Purchase #7	$40.54	7.449%	$43.5598	$43.56	$43.55	$43.60
7 purchase totals =	$898.64		$978.9284	$978.93	$978.90	$978.90