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	$242.41	9.342%	$265.0559	$265.06	$265.05	$265.10
Purchase #2	$38.55	4.310%	$40.2115	$40.21	$40.20	$40.20
Purchase #3	$248.31	4.832%	$260.3083	$260.31	$260.30	$260.30
Purchase #4	$29.70	13.232%	$33.6299	$33.63	$33.65	$33.60
Purchase #5	$213.77	11.670%	$238.717	$238.72	$238.70	$238.70
Purchase #6	$62.70	4.413%	$65.467	$65.47	$65.45	$65.50
Purchase #7	$94.79	12.361%	$106.507	$106.51	$106.50	$106.50
7 purchase totals =	$930.23		$1,009.8966	$1,009.91	$1,009.85	$1,009.90