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	$82.52	8.852%	$89.8247	$89.82	$89.80	$89.80
Purchase #2	$110.86	3.691%	$114.9518	$114.95	$114.95	$115.00
Purchase #3	$171.88	11.298%	$191.299	$191.30	$191.30	$191.30
Purchase #4	$162.29	9.599%	$177.8682	$177.87	$177.85	$177.90
Purchase #5	$58.26	6.535%	$62.0673	$62.07	$62.05	$62.10
Purchase #6	$247.84	5.850%	$262.3386	$262.34	$262.35	$262.30
Purchase #7	$98.78	12.515%	$111.1423	$111.14	$111.15	$111.10
7 purchase totals =	$932.43		$1,009.4919	$1,009.49	$1,009.45	$1,009.50